Interviews with 305 youths (236 males and 69 females) obtained information on demographic characteristics; sexual victimization and physical abuse; family problem characteristics; self-reported alcohol, marijuana, and other illicit drug use; urine testing for recent marijuana and cocaine use; and self-reported delinquent behavior. The study found that the socioeconomic status and composition of the youths' families was much less important in understanding their marijuana/hashish use and delinquency than their families' alcohol, drug abuse, and mental health problems as well as involvement in crime, along with the youths' personal experiences with sexual victimization and physical abuse. These problem issues were related to one another and thus influenced the youths' marijuana/hashish use and delinquent behavior both directly and indirectly. These multiple risk factors increased significantly the likelihood that youths' experiencing them would develop troubled lives. The results suggest an important dynamic in the development of the youths' marijuana/hashish use and delinquent behavior over time. Family problems and abuse/victimization experiences seem to influence the youths' initial involvement in drug use and their delinquent behavior. Once these behavior patterns are established, they tend to continue over time. The findings support the need for prevention and early intervention programs for juvenile detainees. 4 figures, 2 tables, and 53 references