In most parts of the world, some or all aspects of sex work are criminalized. Consequently, sex workers have few legal protections and may easily be exploited or abused by clients, coworkers, and law enforcement officials. The isolation and disempowerment of sex workers, enforced by the threat of violence, may create barriers to negotiating safe sex practices, thereby increasing the risk for human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs). Violence against sex workers by exploitive clients, police, or managers (including pimps) is enabled by a lack of legal protection for sex workers' rights in areas where sex work is criminalized. Understanding the link between violence against sex workers and condom use can be a key to understanding why some sex worker populations are particularly vulnerable to elevated rates of HIV/STI infection compared with the general population, a reality documented in both concentrated and generalized HIV epidemics.1