Research hypotheses and questions focused on the relative influence of different peer factor types, the causal order of peer attitudes and behaviors and respondent behavior, and the influence of developmental changes on these relationships. Results showed that respondents perceived greater levels of drug use among students generally and adolescents in their neighborhoods than among friends. Friend drug use, however, was strongly related to respondent drug use. The causal order of study variables was not necessarily friends influencing respondents but was probably reciprocal. Drug-related behaviors of friends, rather than attitudes, were more strongly related to the likelihood of respondent marijuana initiation. This relationship was strongest for the youngest respondents, those in the sixth grade. The strength of the relationship diminished as adolescents grew older. Recommendations for future research are offered, and implications of the findings for drug use prevention are discussed. 26 references and 9 tables