In-depth interviews were conducted with 24 purposively selected female sex workers who were perceived to be vulnerable to risks associated with their lifestyle and occupation. Brothel workers were found to be considerably less exposed to risk than the women working on the streets. Client resistance was the major obstacle to women maintaining safe sex practices. Physical threats and coercion from clients, the absence of legal protection for street workers, the workers' extreme social isolation and lack of community support added to the difficulties experienced by women in their attempts to insist on condoms for all sex services. Youth, homelessness and heavy drug use had contributed to women being at times even more vulnerable because they had less capacity to manage situations of potential violence or STD risk. Whether through sex work or in their private relationships, HIV remains a risk for some of these women. This study highlights the dangers associated with illegal sex work. While decriminalization of prostitution would reduce some of the dangers to which women were exposed and increase women's capacity to insist on safe sex practices, it is also important for community education programmes to address men's failure to accept responsibility for condom use when seeking the services of sex workers.