Introduction The present research aims to fill a gap in the national and international literature concerning prevalences and factors related to STI (Sexually Transmitted Infections) in Women who Have Sex with Women (WSW).

Methods It is a cross sectional, analytical and non-radomized study with 100 WSW from Botucatu - SP and surrounding regions who answered the call from social media, mass communication means, health services and friends or acquaintances from January to November,2015. Data was obtained by the researchers involved in the main study, through interviews, blood tests to diagnose HIV, syphilis and hepatitis B and cervical sample collection to investigate Chlamydia Trachomatis, Neisseria Gonorrhoeae, HPV through PCR and oncotic cytology to screen Trichomonas vaginalis. Associations were estimated by multiple regression.

Results Total prevalence of STI was 35%, chlamidia infection (3.3%), HIV infection (2.0%), Trichomonas vaginalis (1.1%) and syphilis (1.0%). Neisseria Gonorrhoeae and Hepatites B were not found. The factors associated to STI were: to be single, [OR=3,76 (CI:95%: 1.14–12.43); p=0030], use of sex toys [OR=3,87(CI:95%: 1.14–13.16); p=0030], and number of male partners in the previous year [OR=7,99 (CI:95%: 1.51–42.44); p=0015].

Conclusion Considered as whole, these data lead to conclusion that the individuals of this study presented high vulnerability to STI/AIDS, as shown by the high prevalence of STI. This study clearly shows the need for a specific health assistance to these women, promoting prevention and education in a holistic approach.