The perceived-benefit-of-drinking scale has been developed to assess reasons for drinking in an adolescent population. In this study, the self-administered questionnaire, which has been expanded to include a reason-for-drug-use scale, was completed by 1363 junior and senior high school students. A comprehensive battery of analytic techniques was used to investigate the performance of these perceived-benefit scales on this larger and wider age-range sample. The results confirmed the reliability and validity of the instrument. The findings showed the two scales to perform well across a range of sociodemographic and age groups. These data reassert the strength of the approach and support the instrument's potential as a tool for clinically assessing adolescent substance use.J Dev Behav Pediatr 9:25–29, 1988.Index terms:adolescents, substance abuse, alcohol and drug screening.