This article reviews the extant literature on substance abusers with and without a comorbid diagnosis of post-traumatic stress disorder (PTSD) and reveals the discontinuity between clinical lore and empirical research. Included is an overview of PTSD-substance abuse theoretical models and comorbidity prevalence rates, as well as an evaluation of the comparative data on treatment outcome and psychosocial factors, such as coping skills, for PTSD versus non-PTSD substance abusers. In addition, we discuss the controversy surrounding sequential versus simultaneous treatment approaches for such 'dually-diagnosed' patients. We conclude by identifying gaps in current knowledge about the nature and impact of PTSD on substance abuse treatment outcome and outlining needs for future research.