The study found that although differences in the strength of peer and family influence on adolescent substance use were small in the comparison of rural and urban samples, specific factors within these domains were significant. Adolescents in urban areas did not change their use of overall substance if their families talked about substance use; however, such family conversations actually increased overall substance use by youth in rural areas. Apparently discussing substance use in rural families may increase youths' curiosity about and participation in overall substance use. Youth who lived in urban areas were influenced to use more substances by peers who used alcohol and asked friends to drink alcohol than peers of youth in rural areas. The effect of peer influence for alcohol consumption had no effect on marijuana use by youth in either type of community. That peer influence toward marijuana use had a larger impact on overall substance use for rural youth indicates that, in some cases, peers play a more significant role in rural adolescents' decisions to use substances. Data for this study were obtained from a statewide survey of approximately 4,400 youth in the seventh grade in 17 communities in a Southwestern State. It tested for the inequality of coefficients from regression equations on three measures of substance use: an overall substance use scale, alcohol use, and marijuana use. 4 tables, 5 notes, and 48 references