This study describes the patterns of substance use by male and female gang members in Milwaukee, Wisconsin, from their teenage years in the 1980s into adulthood. Milwaukee gangs started out as one form of neighborhood-based drug-using peer group. There was much variation in drug use, and family variables explained little of the variation. Male gang members raised in families with a history of gang involvement and drug use were more likely than other gang members to use cocaine and to use it seriously. On the other hand, severe family distress was not related to onset, duration, or seriousness of cocaine use in either males or females. Cocaine use for both males and females increased in adulthood. It appears that the etiology of adult and adolescent drug use may differ. Neither social control theory nor differential association theory is well suited to explain the variations in gang drug use by age or gender.