This study explores cross-sectional relationships among childhood sexual abuse (CSA), lifetime traumatic events (LTEs), age at first use of substances, and posttraumatic stress disorder (PTSD) in 644 low-income substance abusing women. History of CSA covaried with earlier age at substance use and higher reported rates of LTEs. Association between first use and LTEs was inconclusive. Both CSA and LTEs predicted PTSD with a partial mediation effect by LTEs. However, first use did not mediate the relationship between CSA and LTEs, rather, CSA directly contributed to increased rates of LTEs.