BACKGROUND. Knowledge of human immunodeficiency virus (HIV) and its risk behaviors have not been systematically studied in homeless mothers. The identification of the factors associated with HIV-risk practices will guide interventions for low-income housed and homeless women. METHODS. We interviewed 220 homeless and 216 low-income housed mothers living in Worcester, Massachusetts, to gather information on demographic, psychosocial, and HIV-risk practice characteristics. We used standardized instruments and questions drawn from national surveys. The primary study outcome was high HIV-risk behavior. RESULTS. Although homeless mothers were more likely than low-income housed mothers to report first sexual contact at an early age, multiple partners during the last 6 months, and a history of intravenous drug use, homelessness was not associated with high HIV-risk practices. Both homeless and low-income housed mothers demonstrated misconceptions about HIV transmission through casual contact. Among high-risk women, approximately 75% perceived themselves as having low or no risk for contracting HIV. A history of childhood victimization, adult partner violence, or both placed women at a significantly increased likelihood of high HIV-risk practices. African American race, knowledge about HIV, and self-perception of risk were also significantly associated with high-risk practices. CONCLUSIONS. Homeless mothers are a subgroup of poor women at high risk for HIV and should be targeted for preventive interventions. In addition, there are potentially modifiable factors associated with HIV-risk practices in both low-income housed and homeless mothers that should be directly addressed. (Authors)