Increasing rates of syphilis, gonorrhea, chancroid, and sexually transmitted human immunodeficiency virus infection appear to be related to crack cocaine use. This article critically reviews 16 epidemiologic studies that examine drug use, sexual behavior, and sexually transmitted disease (STD). Eight studies found an association between crack and STD, one study found no association between crack and STD, and seven studies found STD to be related to other drugs or methods of cocaine use. The exchange of sex for money or drugs was associated with STD in seven studies. Publications that were reviewed have numerous methodologic weaknesses: broader sampling, uninfected comparison groups, and greater specification of drug use and sexual risk behaviors are needed. Further research should compare different drugs and associated sexual behavior and STD to assess the unique risk conferred by crack. Designing effective interventions will require investigation of risk behavior determinants and barriers to health care.