This article describes a unique population within the homeless community--women who are homeless and mentally ill. Homelessness prevalence and etiology data are presented, followed by a general discussion of how mental illness affects people who are homeless. The article provides an overview of women who are homeless, focusing on those who are mentally ill, and discusses the effects of substance use on women. Victimization and its connection to women who are homeless and mentally ill is also examined. We conclude with an integrated comprehensive model of service provision for women who are homeless and mentally ill.