The characteristics of high school student nonmedical drug users and nonusers were assessed by three successive yearly surveys. The surveys asked about respondents' personal, parent, and family characteristics; their behavior; their attitudes concerning themselves; their parents and family, adult society, and school. Drug use estimates for respondents' parents and peers, as well as themselves, were also assessed. Drug users were consistently different from nonusers in many areas. The incidence of drug increased in each of the three successive surveys, drug users tending to be older and male. With regard to behavior, drug users more frequently acted in a nonadult approved manner than nonusers. Drug users estimated their parents more likely to use alcohol and cigarettes, and estimated more peers to use nonmedical drugs than nonusers. Prediction of drug users from the data could be made with 80% and better accuracy. The findings are discussed in terms of their significance in understanding the nature of adolescent drug use.