Social influence and competence variables were associated with having ever used two or more drugs among racial/ethnic minority adolescents residing in inner-city regions. Friends' drinking, friends' smoking, and permissive or ambivalent parental attitudes toward drinking were positively related to poly-drug use across and within gender. Low self-efficacy was positively associated with poly-drug use across gender. Boys who believed that smoking was prevalent among their peers were more likely to engage in poly-drug use. This association did not occur in girls. Girls who believed their friends were against smoking engaged in poly-drug use less frequently. The etiology of drug use among inner-city minority adolescents continues to be an understudied area. Examining theoretically derived models relevant to adolescent drug use may aid in the development and refinement of effective prevention approaches. This study examined social influences to use drugs and competence factors as concurrent predictors of poly-drug use in adolescents, particularly ethnic minority youths who reside in the inner city. The same model was tested separately for boys and girls. The study consisted of 2,400 6th and 7th graders in inner-city schools. Table and references