Although alcohol use has been associated with increased risk of victimization, little is known about how victim substance use at the time of assault may affect posttraumatic stress disorder (PTSD) symptom development. The present study is a longitudinal examination of substance use on PTSD symptom severity and course. A community sample of female crime victims (n = 60) were assessed within 5 weeks of sexual or physical assault with 3 and 6 month postassault follow-ups. Twenty-three participants had consumed alcohol or alcohol/drugs prior to the assault (38%) and 37 had consumed neither alcohol nor drugs. Analyses were conducted using hierarchical linear modeling. Participants who had consumed alcohol had lower initial intrusive symptoms, but their symptoms improved less over time.