The aim of this three-year competitive continuation study is to further improve the psychometric understanding and treatment utility of a recently developed adolescent drug abuse assessment battery, the Personal Experience Inventory (PEI) (Winters & Henly, 1989), and the Adolescent Diagnostic Interview (ADI) (Winters & Henly, 1993). This proposal is motivated by numerous requests from researchers and clinicians that additional psychometric evaluations of the battery would facilitate their work in the prevention and treatment of adolescent drug abuse, and the owing awareness-by the authors that the battery's measurement precision need further study in order to better understand its potential value in adolescent drug treatment research. PEI research will focus on extending reliability and predictive validity evaluations among ethnic/racial minorities and more diverse treatment adolescent samples, expanding school norms, translating test items into Spanish, and validating the questionnaire's six problem screens. ADI research will extend the interview's criterion and predictive validity and examine proposed DSM-IV criteria for substance use disorders. Data analyses will include standard psychometric tests of reliability (e.g., coefficient alpha) and validity (e.g., validity coefficients, kappa), in addition to various multivariate statistics (e.g., LISREL) to further examine scale properties.