In men, those with a chlamydial infection show symptoms of infectious inflammation of the urethra in about 50% of cases. Symptoms that may occur include: a painful or burning sensation when urinating, an unusual discharge from the penis, testicular pain or swelling, or fever. If left untreated, chlamydia in men can spread to the testicles causing epididymitis, which in rare cases can lead to sterility if not treated. Chlamydia is also a potential cause of prostatic inflammation in men, although the exact relevance in prostatitis is difficult to ascertain due to possible contamination from urethritis.

Half of women with gonorrhea do not have symptoms, whereas others have vaginal discharge, lower abdominal pain, or pain with sexual intercourse associated with inflammation of the uterine cervix. Most infected men with symptoms have inflammation of the penile urethra associated with a burning sensation during urination and discharge from the penis. In men, discharge with or without burning occurs in half of all cases and is the most common symptom of the infection. Men and women can acquire gonorrhea of the throat from performing oral sex on an infected partner, usually a male partner. Such infection does not produce symptoms in 90% of cases, and produces a sore throat in the remaining 10%. In advanced cases, gonorrhea may cause a general feeling of tiredness similar to other infections. It is also possible for an individual to have an allergic reaction to the bacteria, in which case any appearing symptoms will be greatly intensified.

The incubation period is 2 to 14 days, with most symptoms appearing between 4 and 6 days after infection. Rarely, gonorrhea may cause skin lesions and joint infection (pain and swelling in the joints) after traveling through the blood stream (see below). Very rarely it may settle in the heart causing endocarditis or in the spinal column causing meningitis (both are more likely among individuals with suppressed immune systems, however).

Having a case of gonorrhea is associated with an increased risk of developing prostate cancer.

Chlamydial infection of the cervix (neck of the womb) is a sexually transmitted infection which has no symptoms for 50–70% of women infected. The infection can be passed through vaginal, anal, or oral sex. Of those who have an asymptomatic infection that is not detected by their doctor, approximately half will develop pelvic inflammatory disease (PID), a generic term for infection of the uterus, fallopian tubes, and/or ovaries. PID can cause scarring inside the reproductive organs, which can later cause serious complications, including chronic pelvic pain, difficulty becoming pregnant, ectopic (tubal) pregnancy, and other dangerous complications of pregnancy.

Chlamydia is known as the "silent epidemic" as in women, it may not cause any symptoms in 70–80% of cases, and can linger for months or years before being discovered. Signs and symptoms may include abnormal vaginal bleeding or discharge, abdominal pain, painful sexual intercourse, fever, painful urination or the urge to urinate more often than usual (urinary urgency).

For sexually active women who are not pregnant, screening is recommended in those under 25 and others at risk of infection. Risk factors include a history of chlamydial or other sexually transmitted infection, new or multiple sexual partners, and inconsistent condom use. Guidelines recommend all women attending for emergency contraceptive are offered Chlamydia testing, with studies showing up to 9% of women aged <25 years had Chlamydia.

Gonorrhea, also spelled gonorrhoea, is a sexually transmitted infection (STI) caused by the bacterium "Neisseria gonorrhoeae". Many people have no symptoms. Men may have burning with urination, discharge from the penis, or testicular pain. Women may have burning with urination, vaginal discharge, vaginal bleeding between periods, or pelvic pain. Complications in women include pelvic inflammatory disease and in men include inflammation of the epididymis. If untreated, gonorrhea can spread to joints or heart valves.

Gonorrhea is spread through sexual contact with an infected person. This includes oral, anal, and vaginal sex. It can also spread from a mother to a child during birth. Diagnosis is by testing the urine, urethra in males, or cervix in females. Testing all women who are sexually active and less than 25 years of age each year as well as those with new sexual partners is recommended; the same recommendation applies in men who have sex with men (MSM).

Gonorrhea can be prevented with the use of condoms, having sex with only one person who is uninfected, and by not having sex. Treatment is usually with ceftriaxone by injection and azithromycin by mouth. Resistance has developed to many previously used antibiotics and higher doses of ceftriaxone are occasionally required. Retesting is recommended three months after treatment. Sexual partners from the last 2 months should also be treated.

Gonorrhea affects about 0.8% of women and 0.6% of men. An estimated 33 to 106 million new cases occur each year, out of the 498 million new cases of curable STI – which also includes syphilis, chlamydia, and trichomoniasis. Infections in women most commonly occur when they are young adults. In 2015, it caused about 700 deaths. Descriptions of the disease date as far back as the Old Testament.

The symptoms of urethritis can include pain or a burning sensation upon urination (dysuria), a white/cloudy discharge and a feeling that one needs to pass urine frequently. For men, the signs and symptoms are discharge from the penis, burning or pain when urinating, itching, irritation, or tenderness. In women, the signs and symptoms are discharge from vagina, burning or pain when urinating, anal or oral infections, abdominal pain, or abnormal vaginal bleeding, which may be an indication that the infection has progressed to Pelvic Inflammatory Disease.

NGU is transmitted by touching the mouth, penis, vagina or anus by penis, vagina or anus of a person who has NGU.

NGU is more common in men than women. Men may have a discharge (strange liquid) from the penis, pain when urinating, and itching, irritation or tenderness around the opening of the penis. Women might not have any symptoms and may not know they have NGU until severe problems occur. Women might have discharge from the vagina, burning or pain when urinating, pain in the abdominal (stomach) area, or bleeding from the vagina that is not from a monthly period. (This may be an sign that NGU has become worse and turned into Pelvic Inflammatory Disease, or PID).

Common symptoms include increased vaginal discharge that usually smells like fish. The discharge is often white or gray in color. There may be burning with urination. Occasionally, there may be no symptoms.

The discharge coats the walls of the vagina, and is usually without significant irritation, pain, or erythema (redness), although mild itching can sometimes occur. By contrast, the normal vaginal discharge will vary in consistency and amount throughout the menstrual cycle and is at its clearest at ovulation—about two weeks before the period starts. Some practitioners claim that BV can be asymptomatic in almost half of affected women, though others argue that this is often a misdiagnosis.

Not all STIs are symptomatic, and symptoms may not appear immediately after infection. In some instances a disease can be carried with no symptoms, which leaves a greater risk of passing the disease on to others. Depending on the disease, some untreated STIs can lead to infertility, chronic pain or even death.

The presence of an STI in prepubescent children may indicate sexual abuse.

Cervices is inflammation of the uterine cervix. Cervicitis in women has many features in common with urethritis in men and many cases are caused by sexually transmitted infections. Death may occur. Non-infectious causes of cervicitis can include intrauterine devices, contraceptive diaphragms, and allergic reactions to spermicides or latex condoms.

The condition is often confused with vaginismus which is a much simpler condition and easily rectified with simple exercises.

Cervicitis can be caused by any of a number of infections, of which the most common are chlamydia and gonorrhea, with chlamydia accounting for approximately 40% of cases. As many half of pregnant women are asymptomatic with a gonorrhea infection of the cervix. "Trichomonas vaginalis" and herpes simplex are less common causes of cervicitis. There is a consistent association of M. genitalium infection and female reproductive tract syndromes. M. genitalium infection is significantly associated with increased risk of cervicitis.

LGV may begin as a self-limited painless genital ulcer that occurs at the contact site 3–12 days after infection. Women rarely notice a primary infection because the initial ulceration where the organism penetrates the mucosal layer is often located out of sight, in the vaginal wall. In men fewer than 1/3 of those infected notice the first signs of LGV. This primary stage heals in a few days. Erythema nodosum occurs in 10% of cases.

The secondary stage most often occurs 10–30 days later, but can present up to six months later. The infection spreads to the lymph nodes through lymphatic drainage pathways. The most frequent presenting clinical manifestation of LGV among males whose primary exposure was genital is unilateral (in 2/3 of cases) lymphadenitis and lymphangitis, often with tender inguinal and/or femoral lymphadenopathy because of the drainage pathway for their likely infected areas. Lymphangitis of the dorsal penis may also occur and resembles a string or cord. If the route was anal sex the infected person may experience lymphadenitis and lymphangitis noted above. They may instead develop proctitis, inflammation limited to the rectum (the distal 10–12 cm) that may be associated with anorectal pain, tenesmus, and rectal discharge, or proctocolitis, inflammation of the colonic mucosa extending to 12 cm above the anus and associated with symptoms of proctitis plus diarrhea or abdominal cramps.

In addition, symptoms may include inflammatory involvement of the perirectal or perianal lymphatic tissues. In females, cervicitis, perimetritis, or salpingitis may occur as well as lymphangitis and lymphadenitis in deeper nodes. Because of lymphatic drainage pathways, some patients develop an abdominal mass which seldom suppurates, and 20–30% develop inguinal lymphadenopathy. Systemic signs which can appear include fever, decreased appetite, and malaise. Diagnosis is more difficult in women and men who have sex with men (MSM) who may not have the inguinal symptoms.

Over the course of the disease, lymph nodes enlarge, as may occur in any infection of the same areas as well. Enlarged nodes are called buboes. Buboes are commonly painful. Nodes commonly become inflamed, thinning and fixation of the overlying skin. These changes may progress to necrosis, fluctuant and suppurative lymph nodes, abscesses, fistulas, strictures, and sinus tracts. During the infection and when it subsides and healing takes place, fibrosis may occur. This can result in varying degrees of lymphatic obstruction, chronic edema, and strictures. These late stages characterised by fibrosis and edema are also known as the third stage of LGV and are mainly permanent.

A woman may have vaginal itching or burning and may notice a discharge.

The discharge may be excessive in amounts or abnormal in color(such as yellow, gray, or green).

The following symptoms may indicate the presence of infection:

- Irritation or itching of the genital area

- inflammation (irritation, redness, and swelling caused by the presence of extra immune cells) of the labia majora, labia minora, or perineal area

- vaginal discharge

- foul vaginal odor

- pain/irritation with sexual intercourse

Urethritis can be caused by mechanical injury (from a urinary catheter or a cystoscope), or by an irritating chemical (antiseptics or some spermicides).

Sexually transmitted infections (STI), also referred to as sexually transmitted diseases (STD) and venereal diseases (VD), are infections that are commonly spread by sex, especially vaginal intercourse, anal sex or oral sex. Many times STIs initially do not cause symptoms. This results in a greater risk of passing the disease on to others. Symptoms and signs of disease may include vaginal discharge, penile discharge, ulcers on or around the genitals, and pelvic pain. STIs can be transmitted to an infant before or during childbirth and may result in poor outcomes for the baby. Some STIs may cause problems with the ability to get pregnant.

More than 30 different bacteria, viruses, and parasites can be transmitted through sexual activity. Bacterial STIs include chlamydia, gonorrhea, and syphilis among others. Viral STIs include genital herpes, HIV/AIDS, and genital warts among others. Parasitic STIs include trichomoniasis among others. While usually spread by sex, some STIs can be spread by non-sexual contact with donor tissue, blood, breastfeeding, or during childbirth. STI diagnostic tests are usually easily available in the developed world, but this is often not the case in the developing world.

The most effective way of preventing STIs is by not having sex. Some vaccinations may also decrease the risk of certain infections including hepatitis B and some types of HPV. Safer sex practices such as use of condoms, having a smaller number of sexual partners, and being in a relationship where each person only has sex with the other also decreases the risk. Circumcision in males may be effective to prevent some infections. Most STIs are treatable or curable. Of the most common infections, syphilis, gonorrhea, chlamydia, trichomoniasis are curable, while herpes, hepatitis B, HIV/AIDS, and HPV are treatable but not curable. Resistance to certain antibiotics is developing among some organisms such as gonorrhea.

In 2015, about 1.1 billion people had STIs other than HIV/AIDS. About 500 million were infected with either syphilis, gonorrhea, chlamydia or trichomoniasis. At least an additional 530 million people have genital herpes and 290 million women have human papillomavirus. STIs other than HIV resulted in 108,000 deaths in 2015. In the United States there were 19 million new cases of sexually transmitted infections in 2010. Historical documentation of STIs date back to at least the Ebers papyrus around 1550 BC and the Old Testament. There is often shame and stigma associated with these infections. The term "sexually transmitted infection" is generally preferred over "sexually transmitted disease" or "venereal disease", as it includes those who do not have symptomatic disease.

Bacterial vaginosis (BV) is a disease of the vagina caused by excessive growth of bacteria. Common symptoms include increased vaginal discharge that often smells like fish. The discharge is usually white or gray in color. Burning with urination may occur. Itching is uncommon. Occasionally, there may be no symptoms. Having BV approximately doubles the risk of infection by a number of other sexually transmitted infections, including HIV/AIDS. It also increases the risk of early delivery among pregnant women.

BV is caused by an imbalance of the naturally occurring bacteria in the vagina. There is a change in the most common type of bacteria and a hundred to thousandfold increase in total numbers of bacteria present. Typically, bacteria other than "Lactobacilli" become more common. Risk factors include douching, new or multiple sex partners, antibiotics, and using an intrauterine device, among others. However, it is not considered a sexually transmitted infection. Diagnosis is suspected based on the symptoms, and may be verified by testing the vaginal discharge and finding a higher than normal vaginal pH, and large numbers of bacteria. BV is often confused with a vaginal yeast infection or infection with Trichomonas.

Usually treatment is with an antibiotic, such as clindamycin or metronidazole. These medications may also be used in the second or third trimesters of pregnancy. However, the condition often recurs following treatment. Probiotics may help prevent re-occurrence. It is unclear if the use of probiotics or antibiotics affects pregnancy outcomes.

BV is the most common vaginal infection in women of reproductive age. The percentage of women affected at any given time varies between 5% and 70%. BV is most common in parts of Africa and least common in Asia and Europe. In the United States about 30% of women between the ages of 14 and 49 are affected. Rates vary considerably between ethnic groups within a country. While BV like symptoms have been described for much of recorded history, the first clearly documented case occurred in 1894.

There are two types of salpingitis: acute salpingitis and chronic salpingitis.

Vaginal infections left untreated can lead to further complications, especially for the pregnant woman. For bacterial vaginosis, these include "premature delivery, postpartum infections, clinically apparent and subclinical pelvic inflammatory disease, [as well as] postsurgical complications (after abortion, hysterectomy, caesarian section), increased vulnerability to HIV infection and, possibly, infertility". Studies have also linked trichomoniasis with increased likelihood of acquiring HIV; theories include that "vaginitis increases the number of immune cells at the site of infection, and HIV then infects those immune cells." Other theories suggest that trichomoniasis increases the amount of HIV genital shedding, thereby increasing the risk of transmission to sexual partners. While the exact association between trichomoniasis infection and HIV genital shedding has not been consistently demonstrated, "there is good evidence that TV treatment reduces HIV genital shedding. Five studies were reported in the literature and, of these, four found a decrease in HIV genital shedding after TV treatment."

Further, there are complications which lead to daily discomfort such as:

- persistent discomfort

- superficial skin infection (from scratching)

- complications of the causative condition (such as gonorrhea and candida infection)

The symptoms usually appear after a menstrual period. The most common are:

- Abnormal smell and colour of vaginal discharge

- Pain during ovulation

- Pain during sexual intercourse

- Pain coming and going during periods

- Abdominal pain

- Lower back pain

- Fever

- Nausea

- Vomiting

- Bloating

Urethritis is inflammation of the urethra. The most common symptom is painful or difficult urination. It is usually caused by infection with bacteria. The bacterial infection is often sexually transmitted, but not in every instance. Urethritis can be idiopathic.

Symptoms in PID range from none to severe. If there are symptoms, then fever, cervical motion tenderness, lower abdominal pain, new or different discharge, painful intercourse, uterine tenderness, adnexal tenderness, or irregular menstruation may be noted.

Other complications include endometritis, salpingitis, tubo-ovarian abscess, pelvic peritonitis, periappendicitis, and perihepatitis.

Tubo-ovarian abscesses (TOA) are one of the late complications of pelvic inflammatory disease (PID) and can be life-threatening if the abscess ruptures and results in sepsis. It consists of an encapsulated or confined 'pocket of pus' with defined boundaries that forms during an infection of a fallopian tube and ovary. These abscesses are found most commonly in reproductive age women and typically result from upper genital tract infection. It is an inflammatory mass involving the fallopian tube, ovary and, occasionally, other adjacent pelvic organs. A TOA can also develop as a complication of a hysterectomy.

Patients typically present with fever, elevated white blood cell count, lower abdominal-pelvic pain, and/or vaginal discharge. Fever and leukocytosis may be absent. TOAs are often polymicrobial with a high percentage of anaerobic bacteria. The cost of treatment is approximately $2,000 per patient, which equals about $1.5 billion annually. Though rare, TOA can occur without a preceding episode of PID or sexual activity.

The signs and symptoms of tubo-ovarian abscess (TOA) are the same as with pelvic inflammatory disease (PID) with the exception that the abscess can be found with magnetic resonance imaging (MRI), sonography and x-ray. It also differs from PID in that it can create symptoms of acute-onset pelvic pain. Typically this disease is found in sexually active women but sexually inexperienced, virginal girls have rarely been found with this infection.

A vaginal obstruction is often caused by an imperforate hymen or, less commonly, a transverse vaginal septum. A sign of vaginal obstruction is hydrocolpos, that is, accumulation of watery fluid within the vagina. It may extend to become "hydrometrocolpos", that is, accumulation of watery fluid within the vagina as well as within the uterus.

Persistent genital arousal disorder (PGAD), which results in a spontaneous, persistent, and uncontrollable genital arousal, with or without orgasm, unrelated to any feelings of sexual desire. Because PGAD is relatively rare and, as its own concept apart from clitoral priapism (a rare, potentially painful medical condition in which, for an unusually extended period of time, the erect clitoris does not return to its relaxed state), has only been researched since 2001, there is little research into what may cure or remedy the disorder. In some recorded cases, PGAD was caused by, or caused, a pelvic arterial-venous malformation with arterial branches to the clitoris; surgical treatment was effective in these cases.

Pelvic inflammatory disease or pelvic inflammatory disorder (PID) is an infection of the upper part of the female reproductive system namely the uterus, fallopian tubes, and ovaries, and inside of the pelvis. Often there may be no symptoms. Signs and symptoms, when present may include lower abdominal pain, vaginal discharge, fever, burning with urination, pain with sex, or irregular menstruation. Untreated PID can result in long term complications including infertility, ectopic pregnancy, chronic pelvic pain, and cancer.

The disease is caused by bacteria that spread from the vagina and cervix. Infections by "Neisseria gonorrhoeae" or "Chlamydia trachomatis" are present in 75 to 90 percent of cases. Often multiple different bacteria are involved. Without treatment about 10 percent of those with a chlamydial infection and 40 percent of those with a gonorrhea infection will develop PID. Risk factors are similar to those of sexually transmitted infections generally and include a high number of sexual partners and drug use. Vaginal douching may also increase the risk. The diagnosis is typically based on the presenting signs and symptoms. It is recommended that the disease be considered in all women of childbearing age who have lower abdominal pain. A definitive diagnosis of PID is made by finding pus involving the fallopian tubes during surgery. Ultrasound may also be useful in diagnosis.

Efforts to prevent the disease include not having sex or having few sexual partners and using condoms. Screening women at risk for chlamydial infection followed by treatment decreases the risk of PID. If the diagnosis is suspected, treatment is typically advised. Treating a woman's sexual partners should also occur. In those with mild or moderate symptoms a single injection of the antibiotic ceftriaxone along with two weeks of doxycycline and possibly metronidazole by mouth is recommended. For those who do not improve after three days or who have severe disease intravenous antibiotics should be used.

Globally about 106 million cases of chlamydia and 106 million cases of gonorrhea occurred in 2008. The number of cases of PID however, is not clear. It is estimated to affect about 1.5 percent of young women yearly. In the United States PID is estimated to affect about one million people yearly. A type of intrauterine device (IUD) known as the Dalkon shield led to increased rates of PID in the 1970s. Current IUDs are not associated with this problem after the first month.