Although an association exists between illicit drug use and sexually transmitted diseases (STDs) in known high-risk populations such as prostitutes, gay men, and intravenous drug users, little is known with respect to middle-class, heterosexual populations thought to be at less risk. We examined findings related to illicit drug use among young adults with genital herpes from a larger study of young adults' adaptation to chronic disease. In this cross-sectional retrospective study, 70 subjects age 18 to 35 years were interviewed and asked to fill out questionnaires. The sample was predominantly white, heterosexual, employed, and college educated. Responses to open-ended questions related to illicit drug use were coded and compared with findings from two other surveys: a national household survey, Pacific region, metropolitan areas; and a household survey of a San Francisco Bay area county. All but eight subjects (88.6%) reported that they had used an illicit drug at some time in the past. The median number of drugs used was 4; the maximum number was 11. Only six drug-using subjects reported that they had restricted their use to marijuana. Those with genital herpes were more likely to report ever using an illicit drug at some time in the past, and, more specifically, in the past year, than subjects in the two comparison surveys. Such findings suggest that programs screen for illicit drug use as a risk factor in middle-class young adults with genital herpes and other STDs, and for STDs in persons referred for drug abuse treatment.