These are diseases transmitted through sexual encounter. Can be transmitted from male to female partner or vice versa and also in homosexuality or lesbianism. These can be of bacterial or viral origin.

Bacterial

Gonococal urethritis:
Males usually having obvious pus coming from the penis. Females have pus but not obvious at the outlet but can easily pass infection to the male partner.

Non- Gonococal urethritis:
Males can later have swelling of the testis and urinary problems with infection of the prostate. Females can have blockage of fallopian tubes and infertility coming up as a complication for life.

If you ever had a premarital or extramarital flick (sex) you must have yourself examined even if you are not having any symptoms.

Lymphogranuloma venerium

Granuloma Inguinale

Chancroid

Syphilis:
It is a systemic disease. May start as small ulcer and destroy the body parts later if untreated .It is a bacterial infection and is treatable provided the treatment is started at the proper time.

Viral

Genital / Anal warts:
Genital and anal warts are the growths most commonly caused by human papilloma virus(HPV 6 to 11). Other type which may be present have been strongly associated with genital dyspilasia and cancer.

Hepatitis B and Hepatitis C:
May also be transmitted sexually and other non-sexual means.