No semi-structured clinical interview currently exists that (a) assesses the severity of DSM-IV and ICD-1O substance use disorders and (b) is designed to he sensitive to changes in clinical status. The Psychiatric Research Interview for Substance and Mental Disorders (PRISM) is a clinician-administered, semi-structured interview that provides reliable diagnoses of drug and alcohol disorders. Preliminary psychometric analyses of PRISM data indicate that the drug and alcohol sections are well-suited for modification into a scale providing continuous severity ratings of DSM- IV and ICD-1O dependence, abuse and harmful use criteria. Thus, development of such a scale is proposed. Phase l work will include (i) literature review and further PRISM-IV data analyses; (2) modification of PRISM items into 6-level items for each criterion; (3) qualitative pilot study of the scale; and (4) development of a training manual. Phase II work would include (i) development of computer software for data entry, data cleaning and derivation of severity scores; (2) development of full training materials; and (3) reliability and validity testing in substance and psychiatric samples, balanced by gender and minority status. This work would constitute further innovation of existing procedures and would have commercial applications in treatment outcome research and the training of clinicians.