The study found significant differences in the pathways through which private religiosity (personal beliefs and values about God and God-oriented behavior) and public religiosity (church attendance and participation in religious activities) influenced the substance-use behaviors of African-Americans. Whereas refusal efficacy significantly mediated private religiosity's effect on tobacco, marijuana, and other illicit substance use, it was not a significant mediator of public religiosity's effect on these same behaviors; however, refusal efficacy was an important pathway through which public religiosity influenced alcohol-use behaviors. One implication of these findings is the value of involving religious institutions in substance-abuse prevention efforts through the development of programs that relate personal beliefs about God to the refusal to abuse substances. Study participants were 435 African-American adolescents and young adults, between ages 12 and 25, from urban (n=186) and rural (n=249) regions of the southeastern United States. The data for this study were obtained while conducting a larger project that examined cultural protective factors against health risks in African-American urban and rural youth. Participants were administered questionnaires that measured demographics, private and public religiosity, refusal efficacy, and substance use. In measuring refusal efficacy, participants were asked to indicate their ability to resist the temptation to use several substances in 10 potentially stressful and pressure situations. The measures of substance use focused on tobacco, alcohol, marijuana, and other illicit drugs such as heroin, crack, and inhalants. 4 tables and 39 references