Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases, remain a growing worldwide problem and public health issue. This article covers the epidemiology of STIs, the history and physical findings, screening guidelines, and the general plan to combat STIs. Prevention is discussed using the latest information from the Centers for Disease Control and Prevention and other references. Infections discussed from the standpoint of cause, epidemiology, risk factors, clinical disease, diagnosis, and treatment include gonorrhea, Chlamydia trachomatis, Trichomonas vaginalis, syphilis, chancroid, Herpes simplex, lymphogranuloma venereum, granuloma inguinale, Herpes papilloma virus, Molluscum contagiosum, and pubic lice.