This study contains data from the second follow-up interview of the Northwestern Juvenile Project (NJP), a longitudinal assessment of alcohol, drug, or mental service treatment needs of juvenile detainees. This second follow-up occurred approximately 3.5 years after the baseline interview and focused on the development and persistence of psychiatric disorders, related predictive variables, patterns of drug use, and other risky behaviors. The project's aims included studying (1) development and persistence of alcohol, drug, and mental disorders and (2) pathways and patterns of risky behaviors. Researchers studied changes in disorders over time (including onset, remission, and recurrence), comorbidity, associated functional impairments, and the risk and protective factors related to these disorders and impairments. The NJP addressed the patterns and sequences of the development of drug use and related variables, focusing on gender differences, racial/ethnic differences, the antecedents of these risky behaviors (risk and protective factors), and how these behaviors are interrelated. The original sample included 1829 randomly selected youth, 1172 males and 657 females, then 10 to 18 years old, enrolled in the study as they entered the Cook County Juvenile Temporary Detention Center from 1995 to 1998. Among the sample were 1,005 African Americans, 524 Hispanics, 296 non-Hispanic white respondents. A random subsample of 997 of the baseline participants were chosen for second follow-up interviews. Researchers tracked participants from the time they left detention and re-interviewed them regardless of where they were living when their follow-up interview was due: in the community, correctional settings, or by telephone if they lived farther than two hours from Chicago. The study was funded by OJJDP, several institutes at the National Institutes of Health, and other federal agencies and private foundations. The National Institutes of Health funded an additional component on HIV/AIDS risk behaviors.