The study reported on structured interviews on self-reported drug use, as well as background variables, social environmental influences, and individual characteristics hypothesized to promote drug use. Logistic-regression analyses revealed that social influences (friends and family drug use) are strong predictors of experimental drug use and intentions to use drugs, as are several psychological factors (psychological well-being, assertiveness, and social support). The only background variable with any predictive power was academic achievement. Study findings suggest that effective prevention programs for homeless and other high-risk youth should: (1) provide an awareness of the various social influences to use drugs; (2) incorporate a broad-based social competency approach which teaches drug-refusal skills, general assertiveness skills, stress and anxiety management techniques, and general social skills; and (3) provide opportunities for gaining peer support by building positive peer groups. Tables, references