OBJECTIVE: To contrast sociodemographic characteristics, physical and mental health status, substance use, sexual behaviors, victimization, and utilization of health services between homeless women residing in sheltered and nonsheltered environments. DESIGN: Cross-sectional survey. A structured scale was used to measure mental health status. Physical health status, substance use, sexual behavior, history of adult victimization, and health services utilization were measured by content-specific items. SETTING: Shelters (N = 47) and outdoor locations in Los Angeles. PARTICIPANTS: One thousand fifty-one homeless women. RESULTS: Homeless women living on the streets were more likely than sheltered women to be white and longer-term homeless. Controlling for sociodemographic characteristics, multiple logistic regression analyses revealed that unsheltered women had over 3 times greater odds of fair or poor physical health, and over 12 times greater odds of poor mental health than sheltered homeless women. They were also more likely than sheltered women to report using alcohol or noninjection drugs, to have multiple sexual partners, and to have a history of physical assault. About half of the overall sample reported utilization of a variety of health services; however, unsheltered homeless women were less likely to utilize all of the health services that were assessed, including drug treatment. CONCLUSIONS: There is a critical need for aggressive outreach programs that provide mental health services and substance abuse treatment for homeless women on the streets. Comprehensive services that also include medical care, family planning, violence prevention, and behavioral risk reduction may be particularly valuable for homeless women, especially those living in unsheltered environments.