A cross-sectional survey was conducted of sexually transmitted diseases (STDs) and risky behaviors among 407 drug abusers in treatment facilities in 1998. Infections with human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), herpes simplex virus type 2 (HSV-2), and syphilis were detected by testing serum antibody levels; chlamydia and gonorrhea were detected by testing nucleic acid levels in urine. Logistic regression analysis was performed to measure associations. Prevalences of antibodies were as follows: to HSV-2, 44.4%; to HCV, 35.1%; to HBV, 29.5%; to HIV, 2.7%. The prevalence of syphilis was 3.4%; of chlamydia, 3.7%; and of gonorrhea, 1.7%. Of the 407 subjects, approximately 62% had markers for 1 of the STDs. HIV infection was associated with African American race, use of smokable freebase (crack) cocaine, and STD history. HBV infection was associated with age >30 years, injecting drugs, needle sharing, a history of treatment for drug abuse, and African American race. HCV infection was associated with an age >30 years, injecting drugs, and needle sharing, and HSV-2 infection with an age >30 years, female sex, and African American race. Syphilis was associated with a history of STDs. High prevalences of STDs among drug abusers indicate the need for integration of STD screening and treatment into drug treatment programs.