Reduction of problem behaviors (drug and alcohol use, school problems, and legal involvement) by Mexican-American youth (N = 326) during their first 3 months in drug abuse intervention programs was related negatively to peer drug use during the program and was related positively to the amount of family support available during the program, participation in program activities, and a background of religious involvement. These findings support previous research that has shown the importance of peer influences and commitment to conventional structures of family and religion in relation to adolescent problem behaviors. These findings suggest that two goals that adolescent drug abuse programs should stress are working heavily on developing positive peer relations and family support while they encourage disassociation from deviant friends.