Abstract:Background: Sex workers are disproportionately affected by HIV and other STIs compared with the general population. To date, most studies of HIV risk among sex workers focus on individual-level risk factors, with few studies evaluating potential structural determinants of HIV risk. In this paper we examine whether criminal laws around sex work are associated with HIV prevalence among sex workers.Method: To test our hypothesis, we estimate cross-sectional, ecological regression models using data from 27 European countries on HIV prevalence among sex workers from the European Centre for Disease Control; sex-work legislation on U.S. State Department's Country Reports on Human Rights Practices; the Rule of Law and GDP per capita, adjusted for purchasing power, from the World Bank; and the prevalence of injection drug use among sex workers.Findings: We found that countries which have legalised some aspects of sex work (n = 10) have significantly lower HIV prevalence among sex workers than those which have not (n = 17) (β = -2.09, 95% CI: -0.80 to -3.37, p = 0.003), even after controlling for the level of economic development and the proportion of sex workers who are injecting drug users.