Few studies in Africa provide detailed descriptions of the vulnerabilities of female sex workers (FSW) to sexual and physical violence, and how this impacts on their HIV risk. This qualitative study documents FSW's experiences of violence in Mombasa and Naivasha, Kenya. Eighty-one FSW who obtained clients from the streets, transportation depots, taverns, discos and residential areas were recruited through local sex workers trained as peer counsellors to participate in eight focus-group discussions. Analysis showed the pervasiveness of sexual and physical violence among FSW, commonly triggered by negotiation around condoms and payment. Pressing financial needs of FSW, gender-power differentials, illegality of trading in sex and cultural subscriptions to men's entitlement for sex sans money underscore much of this violence. Sex workers with more experience had developed skills to avoid threats of violence by identifying potentially violent clients, finding safer working areas and minimising conflict with the police. Addressing violence and concomitant HIV risks and vulnerabilities faced by FSW should be included in Kenya's national HIV/AIDS strategic plan. This study indicates the need for multilevel interventions, including legal reforms so that laws governing sex work promote the health and human rights of sex workers in Kenya.