A qualitative research approach was used to explore the factors that influence the initiation of drug and alcohol use among homeless women and the health and social consequences of drug and alcohol use. The sample consisted of 238 women; of whom 209 women reported drug and/or alcohol use in the past month and 29 women reported no history of drug or alcohol use. Findings of the study revealed homeless women who currently used drugs and alcohol, homeless women who currently used drugs only, and to a lesser extent current alcohol users only, had suffered traumatic childhood events and family dysfunction and had to cope with low self-esteem, emotional distress, and poor physical health. The initiation of drug and/or alcohol use was strongly affected by the social influence of other users. In comparison, homeless women who did not use drugs or alcohol reported a positive self-image, few traumatic events, and chose partners who did not use drugs or alcohol. Common among current drug and/or alcohol users were the reported social benefits of drug use. Quantitative analyses revealed homeless women who were current drug users were significantly more likely to have experienced childhood and adult victimization as compared with women in the other groups. Thus, the need for social interventions and positive social support early in the lives of these women are strongly implicated in these findings.