This study examines understandings of sexual and reproductive health and healthcare, and perceptions of health services among women who regularly or occasionally sell or transact sex in Escuintla, Guatemala. Using an approach informed by grounded theory, 35 individual interviews were analysed. Results suggest that sex workers face multiple forms of vulnerability due to their level of education, economic situation and unequal gender relations. Many feel dissatisfied with the quality of health services received, specifically with the lack of medicines, poor personal treatment by health workers and scanty information. Condoms were widely acknowledged as the means of preventing STI/HIV; however, many of the women do not use them with regular clients and regular partners. An effective STI/HIV-prevention strategy that addresses sex workers' circumstances and needs, requires a comprehensive approach, which includes a combination of individual and community-based interventions. These interventions must involve clients, sex establishment owners and health personnel.