Background. Youth substance use began to increase in 1992 following a decade-long decline, leading to increased interest in controlling access to tobacco, alcohol, and other drugs. Methods. The anonymous and voluntary Minnesota Student Survey was administered to 133, 794 public school students in grades 6, 9, and 12. Questions addressed current frequency of use of tobacco, alcohol, and other drugs and how students obtained these substances. Data were analyzed to determine the relationship between grade level, gender, race/ethnicity, use frequency, and access to substances through social and commercial sources. (Tobacco analyses were limited to students under age 18 years.) Results. Social sources (especially friends) predominate across all age groups and substances. Students are much more likely to obtain tobacco than alcohol from commercial sources but few rely exclusively on commercial sources for either. Females and infrequent users are more likely to depend on social sources exclusively while males and frequent users are more likely to use commercial sources. Conclusions. Because substances are easily accessible through social sources, prevention policies directed at retail outlets may not have the desired effect on reducing teen smoking and drinking. Greater attention to reducing access to all substances from social sources is needed.