OBJECTIVE We sought to explore the reach of a free hepatitis B vaccination program among female commercial sex workers (CSWs) within a legalized prostitution setting in the Netherlands. We also investigated the reasons for nonparticipation and noncompliance. METHODS In this cross-sectional study based on ethnographic mapping and targeted sampling, 259 CSWs were interviewed at their work in 3 regions in the Netherlands. The semistructured interviews contained questions on sociodemographics, sexual risk behavior, sex work, awareness of the opportunity to obtain free hepatitis B vaccination, vaccination uptake, and compliance with the full vaccination schedule. RESULTS Of our sample, 79% reported awareness of the opportunity to obtain hepatitis B vaccination, and 63% reported to be vaccinated against hepatitis B (received > or =1 vaccination). A personal approach by health professionals or was associated with vaccination uptake, when specific sociodemographic variables, sexual behavior, and sex work related covariates were controlled for in the analysis. Window prostitution and the duration of working in the region were associated with awareness of the opportunity to obtain free hepatitis B vaccination. CONCLUSIONS The results of this study suggest that outreach activities (i.e., a personal approach) within this program are beneficial. Transient CSWs are more difficult to reach within the current vaccination program. These results can be used to increase the success of future health programs among this risk group.