We propose to exploit a large, longitudinal data set collected from successive cohorts of high school seniors since 1976 in order to examine the relationhships of self-reported illegal behavior to some of the major role transitions which characterize late adolescence and early adulthood. The data were collected as part of the Monitoring the Future study, which has as its primary focus the examination of the prevalence, trends, and explanations of drug usage among young people, but which also asks a set of questions about a variety of non-drug related illegal behaviors. Each year, nationally representative samples of 17,000 to 18,000 high school seniors in public and private schools complete self- administered questionnaires. Subsamples of each class are also asked to complete follow-up questionnaires every two years for ten years following graduation, thereby providing panel data about illegal behavior over the age range of approximately 18 to 28. At least three waves of data on illegal behavior are available for over 3,000 respondents who graduated from high school in 1976 through 1982. At each data collection, respondents report on their work and marital statuses, their living arrangements, and their participation in a wide range of leisure activities. We propose to examine changes in the rate of participation in illegal activities that may be caused by changes in these lifestyle variables. The data constitute a rich source of information about the involvement of young people in legal as well as illegal activities. They will provide both valuable descriptive information about age patterns and the opportunity to relate measures of illegal activity to important characteristics and events in the lives of young people. The fact that the data have been collected using a panel design, and from a series of successive cohorts, makes them especially valuable for the essentially exploratory type of analyses that we propose, and which seem to us to be highly appropriate for developing new theories or refining old ones.