The research emphasized gender and peer-group differences in these settings, the settings associated with more problematic use of alcohol and drugs, and the settings that potentially served as sites of initiation of adolescent substance use. The participants were ages 16-19 years; 51 percent were males. They completed the surveys in class. Results revealed few gender differences in the settings of substance use, although females were more likely than males to drink alcohol in family settings. More severe substance use was associated with a higher likelihood of drinking at school. Moreover, alcohol users were more likely to report drinking in their own homes and at their friends’ homes than abstainers were to indicate selecting these settings to use alcohol if they were to do so. Drug users were more likely to report substance use outdoors, at their friends’ homes, at social parties, and at school than were abstainers to indicate selecting these settings to use drugs if they were to do so. Findings suggested that the setting where substance use occurs may be important in examining differences among individual substance users, in evaluating the severity of substance use, and in identifying settings to target to prevent drug abuse among youth. Table and 29 references (Author abstract modified)