Purpose. This study assessed lifetime and current prevalence rates of mental disorders and concurrent mental and substance use disorders in a sample of homeless women. Current suicide risk and recent health service utilization were also examined in order to understand the complex mental health issues of this population and to inform the development of new treatment strategies that better meet their specific needs. Methods. A cross-sectional survey of 196 adult homeless women in three different Canadian cities was done. Participants were assessed using DSM-IV-based structured clinical interviews. Current diagnoses were compared to available mental health prevalence rates in the Canadian female general population. Results. Current prevalence rates were 63% for any mental disorder, excluding substance use disorders; 17% for depressive episode; 10% for manic episode; 7% for psychotic disorder; 39% for anxiety disorders, 28% for posttraumatic stress disorder; and 19% for obsessive-compulsive disorder; 58% had concurrent substance dependence and mental disorders. Lifetime prevalence rates were notably higher. Current moderate or high suicide risk was found in 22% of the women. Participants used a variety of health services, especially emergency rooms, general practitioners, and walk-in clinics. Conclusion. Prevalence rates of mental disorders among homeless participants were substantially higher than among women from the general Canadian population. The percentage of participants with moderate or high suicide risk and concurrent disorders indicates a high severity of mental health symptomatology. Treatment and housing programs need to be accompanied by multidisciplinary, specialized interventions that account for high rates of complex mental health conditions.