The subjects were 1,687 adolescents who lived in mixed urban-rural communities in Colombia. Individual interviews were administered to youths in their homes by Colombian interviewers. The scales used were based on item intercorrelations grouped into the following risk categories: adolescent personality, family traits, peer factors, and cultural/ecological variables. Pearson correlations were computed for each variable and the frequency of marijuana use. Results show that each of the domains was related to adolescent marijuana use, with some notable gender differences. Regarding the interrelation of domains, a mediational model was operative. The findings support a family interactional theory. The domains of family, personality, and peer factors had a direct effect on the adolescents' marijuana use. The study concludes that each of the domains (culture/ecology, family, personality, and peer) is a potential focus for intervention; multiple interventions may be indicated, because there are multiple direct and indirect paths to drug use; the direct and indirect influences of culture/ecology and family suggest intervening early in the developmental path that leads to drug use; and prevention or treatment programs developed in Colombia may use findings from research on the etiology of drug use conducted in the United States. 2 tables, 1 figure, and 32 references