We evaluated mobile street-based outreach as a modality for linking street-walking female sex workers with substance abuse treatment in New York City. Sex workers (N = 179) approaching an existing outreach facility were randomly assigned to receive usually provided services, or to receive an enhanced version of these services. Among the 144 women successfully followed for 6 months, 35.0% were detoxified; 43.1% of the 78 current heroin users received methadone maintenance; and 35.4% of the followed-up clients received some other type of treatment. Intervention group differences in these outcomes were not significant. Detoxification during followup was associated with heroin dependence and lifetime detoxification. Methadone maintenance (among heroin users) was associated with Hispanic ethnicity and legally mandated treatment. Other types of treatments were negatively associated with the degree of involvement in the sex trade. We conclude that a variety of factors affect motivation for substance abuse treatment among female sex workers, and that street-based outreach is a highly effective modality for linking this population with much needed treatment.