Inviting the help of colleagues worldwide, the concise Diagnostic Issues in Substance Use Disorders is part of the new series, Advancing the Research Agenda for DSM-V. Its 19 chapters by an international group of experts are designed to stimulate questions that will help guide research related to the development of the next editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) and the International Classification of Diseases (ICD-11), with the goal of ensuring that the major substance use diagnoses represent the same condition in both references. These 19 chapters cover 10 major issues: categorical versus dimensional diagnoses, the neurobiological basis of substance use disorders, social and cultural perspectives, the crosswalk between DSM-IV and ICD-10, comorbidity of substance use disorders and mental health disorders, subtypes of disorders, issues in adolescence, substance-specific criteria, the place of non-substance-related addictive disorders, and available research resources. The conclusion presents a broadly based research agenda for developing diagnostic concepts and criteria for substance use disorders. This deeply informative compendium distills the work done from 2002 to late 2005 and concludes with recommendations for developing research activities that will inform DSM-V and future editions of the manual. As such, it will prove invaluable for clinicians and researchers everywhere.