The aim of this study was to determine whether possession of a driver's license increases the risk of impaired driving among adolescents who use alcohol or marijuana. An anonymous questionnaire was administered to secondary school students in northeast Ohio across multiple school districts. Logistic regression analyses revealed that after accounting for socio-demographic variables, legal driving privileges were independent risk factors for both alcohol- and marijuana-impaired driving, and more robust than substance use in distinguishing between impaired and non-impaired drivers. Prevention strategies must address conventional licensing policies in addition to social and contextual factors leading to adolescent alcohol and marijuana use and associated risks. (Contains 2 tables.)