Changes in the profile of sexually transmitted diseases have increased the need for their detection, particularly where there is a concentration of individuals with risk behavior, so that diagnosis and immediate treatment can be translated in the reduction of resulting problems. The objective was to identify the prevalence of sexually transmitted diseases in female sex workers in a medium-sized city in São Paulo state. This population prevalence study was conducted in 2008 on 102 females. The prevalence was 71.6%. When considered separately and in association, the highest values found were: HPV (67.7%) and Chlamydia (20.5%). HPV typing showed oncogenic genotypes. The prevalence of syphilis was 4.0% and of trichomoniasis 3.0%. No cases of hepatitis B or gonorrhea were identified. It was concluded that the prevalence of sexually transmitted diseases in the studied group was high, since approximately two thirds of the women showed some type of disease under this classification. Considerados aisladamente y en asociación, los mayores valores encontrados fueron: VPH (67,7%) e infección clamidiana (20,5%). El tipaje del VPH evidenció genotipos oncogénicos. La prevalencia de sífilis fue de 4,0% y de tricomoníasis 3,0%. Ningún caso de hepatitis B o gonorrea fue identificado. Se concluye que la prevalencia de enfermedad sexualmente transmisible fue elevada, ya que aproximadamente dos tercios de las mujeres presentaban alguna enfermedad de ese tipo.