Little is known about how adolescents' peer relations might alter whether sport participation is associated with alcohol use. Consistent with social learning theory, we found that sport participation was protective against alcohol use if these peers had low alcohol use, but athletes were likely to use alcohol if their sport friends and teammates had high alcohol use. Interestingly, those with no or low sport participation seemed to emulate the alcohol use of their non-sport friends, whereas adolescents in a high number of sports had elevated alcohol use regardless of their non-sport friends' alcohol use. (Contains 1 table and 3 figures.)