In a sample of 336 patients with an alcohol use disorder, this study examined, whether patients with histories of childhood sexual abuse (CSA) and childhood physical abuse (CPA) compared to those without such histories have a greater severity of alcohol and other clinical difficulties. Whether lifetime posttraumatic stress disorder (PTSD) mediates the relationship between childhood abuse and clinical outcomes was explored. Results were that CSA was associated with earlier age of onset for alcohol disorder, greater Axis I comorbidity as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV; American Psychiatric Association, 1994), more social and psychiatric problems, but lower drinking frequency. Childhood physical abuse was related to greater drinking consequences, social and psychiatric dysfunction, and Axis I comorbidity, but also lower drinking frequency. Posttraumatic stress disorder partially mediated the effect of both CSA and CPA on severity of psychiatric problems.