We examined condom breakage rates and predictors of breakage in a prospective telephone-based study of female sex workers (FSWs) in Bangalore, India. We obtained data on 3,257 condom-use sex acts, and breakage occurred in 2.1 % of these. Situational factors, especially those associated with male clients' behaviors, were the most important predictors of breakage, including sexual inexperience, roughness and violence. Breakage was also associated with having vaginal and anal sex at the same encounter and with poor-fitting condoms. Despite lower than expected breakage rates, the high client volume of FSWs means that there are many unprotected sex acts caused by breakage. Discussions should be held around new education messages, and how programs can respond quickly when sex workers encounter clients who are inebriated, violent or unusually sexually charged. More work is urgently needed with police, and on FSW empowerment, the use of help lines, and counseling for the most vulnerable women.