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.

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.

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.

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).

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.

Nongonococcal urethritis (NGU) is an inflammation of the urethra that is not caused by gonorrheal infection.

For treatment purposes, doctors usually classify infectious urethritis in two categories: gonococcal urethritis, caused by gonorrhea, and nongonococcal urethritis (NGU).

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 clinical manifestation of LGV depends on the site of entry of the infectious organism (the sex contact site) and the stage of disease progression.

- Inoculation at the mucous lining of external sex organs (penis and vagina) can lead to the inguinal syndrome named after the formation of buboes or abscesses in the groin (inguinal) region where draining lymph nodes are located. These signs usually appear from 3 days to a month after exposure.

- The rectal syndrome arises if the infection takes place via the rectal mucosa (through anal sex) and is mainly characterized by proctocolitis symptoms.

- The pharyngeal syndrome is rare. It starts after infection of pharyngeal tissue, and buboes in the neck region can occur.

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

In males, the lesions occur on the glans penis, shaft of the penis or other parts of the genital region, on the inner thigh, buttocks, or anus. In females, lesions appear on or near the pubis, clitoris or other parts of the vulva, buttocks or anus.

Other common symptoms include pain, itching, and burning. Less frequent, yet still common, symptoms include discharge from the penis or vagina, fever, headache, muscle pain (myalgia), swollen and enlarged lymph nodes and malaise. Women often experience additional symptoms that include painful urination (dysuria) and cervicitis. Herpetic proctitis (inflammation of the anus and rectum) is common for individuals participating in anal intercourse.

After 2–3 weeks, existing lesions progress into ulcers and then crust and heal, although lesions on mucosal surfaces may never form crusts. In rare cases, involvement of the sacral region of the spinal cord can cause acute urinary retention and one-sided symptoms and signs of myeloradiculitis (a combination of myelitis and radiculitis): pain, sensory loss, abnormal sensations (paresthesia) and rash. Historically, this has been termed Elsberg syndrome, although this entity is not clearly defined.

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)

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.

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.

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.

The signs and symptoms of a vertically transmitted infection depend on the individual pathogen. It may cause subtle signs such as a influenza-like illness and may not even be noticed by the mother during the pregnancy. In such cases, the effects may be seen first at birth.

Symptoms of a vertically transmitted infection may include fever and flu like symptoms. The newborn is often small for gestational age. A petechial rash on the skin may be present, with small reddish or purplish spots due to bleeding from capillaries under the skin. An enlarged liver and spleen (hepatosplenomegaly) is common, as is jaundice. However, jaundice is less common in hepatitis B because a newborn's immune system is not developed well enough to mount a response against liver cells, as would normally be the cause of jaundice in an older child or adult. Hearing impairment, eye problems, mental retardation, autism, and death can be caused by vertically transmitted infections. The mother often has a mild infection with few or no symptoms.

The genetic conditions of Aicardi-Goutieres syndrome are possibly present in a similar manner.

A genital ulcer is located on the genital area, usually caused by a sexually transmitted disease such as genital herpes, syphilis, chancroid, or "Chlamydia trachomatis". Some other signs of having genital ulcers include enlarged lymph nodes in the groin area, or vesicular lesions, which are small, elevated sores or blisters. The syndrome may be further classified into penile ulceration and vulval ulceration for males and females respectively.

Genital ulcers are not strictly a sign of an STD. They can occur in patients with Behcet's syndrome, lupus, and some forms of rheumatoid arthritis (all non-communicable diseases). Genital tuberculosis, often caused by direct genital contact with infected sputum, can also present as genital ulcer.

Genital herpes is an infection by herpes simplex virus (HSV) of the genitals. Most people either have no or mild symptoms and thus do not know they are infected. When symptoms do occur, they typically include small blisters that break open to form painful ulcers. Flu-like symptoms may also occur. Onset is typically around 4 days after exposure with symptoms lasting up to 4 weeks. Once infected further outbreaks may occur but are generally milder.

The disease is typically spread by direct genital contact with the skin surface or secretions of someone who is infected. This may occur during sex including oral sex. Active sores are not required for transmission to occur. HSV is classified into two types, HSV-1 and HSV-2. While historically mostly cause by HSV-2, genital HSV-1 has become more common in the developed world. Diagnosis may occur by testing lesions using either PCR or viral culture or blood tests for specific antibodies.

Efforts to prevent infection include not having sex, using condoms, and only having sex with someone who is not infected. Once infected their is no cure. Antiviral medications may, however, prevent outbreaks or shorten outbreaks if they occur. The long term use of antivirals may also decrease the risk of further spread.

In 2015 about 846 million people (12%) had genital herpes. Women are more commonly infected than men. Rates of disease caused by HSV-2 have decreased in the United States between 1990 and 2010. Complications may rarely include aseptic meningitis, an increased risk of HIV/AIDS if exposed, and spread to the baby during childbirth resulting in neonatal herpes.

A vertically transmitted infection can be called a perinatal infection if it is transmitted in the perinatal period, which is the period starting at a gestational age of between 22 and 28 weeks (with regional variations in the definition) and ending seven completed days after birth.

The term congenital infection can be used if the vertically transmitted infection persists after childbirth.

The infection usually has its origin in the vagina and ascends to the Fallopian tube from there. Because the infection can spread via the lymph vessels, infection in one Fallopian tube usually leads to infection of the other.

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

Penile discharge is fluid that comes from the urethra at the end of the penis. This may occur with infections due to gonorrhea, chlamydia, or trichomoniasis. In gonorrhea the discharge may by white, yellow, or green.