Attachment refers to the extent to which people are bonded to individuals, groups, and institutions within society that support conventional values and norms. Attachment is hypothesized to be an important deterrent to alcohol use and other forms of delinquency. Consistent with this assumption, positive child-parent relations have been associated with low levels of drinking. Opportunity is a second sphere of influence, rooted in both parental and peer relationships, that has potential relevance to alcohol use and abuse among adolescents. Presumably, individuals who engage in shared activities with their parents and whose interactions with peers are in the context of conventional institutions (e.g., school or church) have less free time within which to engage in deviant behavior. In the current study, attachment was measured by adding respondents' scores on six NELS items that focused on how well they liked and got along with their parents. The extent to which individuals' peers supported alcohol use was measured by using students' responses to a question about how important it was to be "willing to party or get wild" among their friends. Respondents' opportunities for alcohol use and heavy drinking were measured by using five indexes: participation in unstructured peer interaction, participation in structured (extracurricular) activities, time spent with parents, parental monitoring, and parental control. Questions about students' drinking behaviors, measured during the senior year of high school, provided data on the key dependent variable for the analysis. Overall, the study findings indicated that peers were more influential than parents in shaping adolescents' patterns of alcohol consumption, with unstructured peer interaction being an especially powerful predictor of adolescent alcohol use and binge drinking. The findings further suggested that gender was a conditioning factor, moderating the effects of parental and peer variables on high school students' drinking. Potential programmatic applications as well as the theoretical implications of these findings are discussed in the context of control theory and prior research on the relationship between opportunity and delinquency. 5 figures, 3 tables, and 60 references