Aims of the study were to identify social conditions, personal characteristics, and developmental patterns that were linked to sustained involvement in juvenile delinquency and drug use and to examine the relationship between developmental patterns and behaviors and mental health and victimization. The study focused extensively on female delinquency, neighborhoods, school environments, mental health issues, gang involvement, problem drug use, and victimization. It was based on a probability sample of households in high-risk neighborhoods in the Denver area. Study respondents included 1,527 children and youths (806 boys and 721 girls) who were 7, 9, 11, 13, or 15 years old in 1987 and one of their parents. The sampling procedure resulted in the inclusion of a large number of black, Hispanic, and other minority youth. Interview schedules included measures to assess juvenile delinquency and drug use, problem behavior and other psychopathology, family demographics, neighborhood social characteristics and family integration and support, youth involvement in school and community activities, youth involvement in religious activities and work, personal and psychological characteristics of youth, medical histories, and involvement with delinquent peers. General study findings are presented according to five categories: (1) epidemiology of juvenile delinquency, drug use, and victimization; (2) peers and delinquent gangs; (3) explanatory, risk, and protective factors: (4) impact of arrest on subsequent delinquent behavior; and (5) help-seeking for psychological and behavioral problems, including juvenile delinquency. References and tables