This study examined the correspondence between parent and adolescent reports of the adolescent's substance use in a population of parents concerned about, and experiencing problems resulting from, their teen's substance use. Seventy-five parents and their adolescents (76% not in treatment; 24% in treatment) were interviewed separately regarding the teen's recent use of cigarettes, alcohol, marijuana, and other illicit drugs. Irrespective of adolescent treatment status, fair-to-good congruence was found on cigarette and marijuana use, alcohol use frequency, and overall substance use frequency. Poor congruence was found on the incidence of alcohol and other illicit drug use, and the quantity of alcohol consumed per drinking day. Multiple regression analysis revealed that poorer congruence on substance use frequency occurred when the teen was younger, when the parent scored low on monitoring and high on psychological distress, and when the parent used alcohol more frequently. Results indicate that parental awareness of teen substance use varies with the substance used and its measurement. In the absence of a cooperative teen, however, parental report of the frequency of adolescent substance use appears to serve as a fair-to-good proxy.