Participants represented various groups interested in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) for data analysis. The Diagnostic Work Group identified several issues for discussion that focused on lumping versus splitting criteria, physiological subtypes, duration or clustering, and differences between drug dependence and drug abuse. The Severity Work Group pursued the development and validation of methods for scaling the severity of dependence for all substance abuse disorders. Selected findings from DSM-IV substance abuse field trials and from the National Health Interview Survey related to alcohol use and alcohol-related problems were summarized. The meeting also considered the Yale/University of Connecticut study of diagnostic criteria, alcoholism diagnostic issues in a clinical sample, severity issues relevant to the DSM-IV, studies of the diagnosis and severity of substance abuse disorders, and critical issues in the diagnosis of substance abuse disorders. Finally, meeting participants summarized findings from the 1990 National Alcohol Survey in terms of DSM-IV criteria. 26 references, 10 tables, and 14 figures