OBJECTIVE: To measure prevalence of HIV and syphilis and describe characteristics of sex work among female sex workers (FSWs) in Hargeisa, Somaliland, Somalia. METHODS: A cross-sectional survey recruited 237 FSWs using respondent-driven sampling (RDS). A face-to-face, structured interview using handheld-assisted personal interviewing (HAPI) on personal digital assistants (PDAs) was completed and blood collected for serological testing. RESULTS: FSWs 15-19 years old accounted for 6.9% of the population; 20-24 year-old constituted an additional 18.0%. The majority (86.6%) never attended school. International (59.0%) and interzonal (10.7%) migration was common. Most (95.7%) reported no other source of income; 13.8% had five or more clients in the last 7 days. A minority (38.4%) had heard of STIs, even fewer (6.9%) held no misconceptions about HIV. Only 24% of FSW reported using a condom at last transactional sex, and 4% reported ever been tested for HIV. HIV prevalence was 5.2% and syphilis prevalence was 3.1%. CONCLUSION: Sex work in Hargeisa, Somaliland, Somalia, is characterized by high numbers of sexual acts and extremely low knowledge of HIV. This study illustrates the need for targeted HIV prevention interventions focusing on HIV testing, risk-reduction awareness raising, and review of condom availability and distribution mechanisms among FSWs and males engaging with FSWs.