The objective of this prospective follow-up study was to examine the effects of sexual abuse on substance use disorder patients' clinical presentation and course in treatment. Consecutive admissions to the MUHC's Addictions Unit were assessed at intake (N=206) and six-month follow-up (n=172). Assessments evaluated socio-demographic and psychiatric characteristics, addiction severity, and physical and/or sexual abuse histories. Upon entering treatment, 23% reported prior sexual abuse with or without physical abuse. Patients with a sexual abuse history had higher rates of psychological problems, stronger family histories of substance use disorders, and more impaired family relationships. At six months, there were no differences between patients with and without sexual abuse histories in their response to treatment, or their utilization of treatment services. The current study failed to show that prior sexual abuse compromised short-term treatment outcomes.