In this retrospective review of cases of clinical proctitis, we identified the frequency of common sexually transmitted diseases (STDs) among men who have sex with men on the basis of reports from the municipal STD clinic in San Francisco. Of note, gonorrhea and chlamydia were the most common STDs, followed by herpes and syphilis. Current STD treatment guidelines recommend empiric treatment for gonorrhea and chlamydia, but treatment for herpes should also be considered. The implications for human immunodeficiency virus (HIV) transmission are also discussed.