The association of trauma and posttraumatic stress disorder (PTSD) with alcohol and cocaine use is explored to determine if there is additive risk associated with dual dependence. Data were collected from out-of-treatment women enrolled in an HIV-prevention study. Women who experienced a DSM-IV qualifying event (n = 791) were stratified into four substance use groups based on lifetime alcohol and cocaine use. Women with lifetime comorbid alcohol and cocaine dependence experienced significantly more traumatic events and had a higher prevalence of violent events and lifetime diagnosis of PTSD and PTSD-related impairment. There is added risk for associated trauma and subsequent PTSD among women who have dual substance dependence.