We propose to continue the analysis of data already collected and partly analyzed on a nationwide sample of 2,510 young men, and to begin the analysis of data collected on a sample of 300 young men from high drug use areas in Manhattan, New York City. Both were multi-stage stratified probability samples of their respective populations, drawn from Selective Service records, and data were collected by interview. Original research questions related to the natural history of drug use, estimates of incidence and prevalence, the drug epidemic of the late 1960's, and correlates of differences in these areas. Emphasis in analysis of the nationwide data has been descriptive, with respect to the last three of these four questions; future analysis will be more oriented to explanation, and to the natural history of use, especially in the identification of patterns of use over time and their relations to life events. The New York interview was more theoretically than descriptively oriented, with an increased emphasis on heroin use. The major interest here is in testing theoretical explanations of heroin use, including anomie, differential association, social control and labelling theories.