Introduction There is scarce data concerning epidemiology and demography of Sexually Transmitted Infections (STIs) in Brazil, in spite of their high prevalence. Moreover, there are only a few specialised centres for diagnosis and treatment. The Sexually Transmitted Diseases Combat Service (SCDST) was founded 30 years ago by medical students from UNIFESP-EPM and has maintained ever since an ambulatory specialised in diagnostics, treatment and follow-up for roughly thirty patients every week. In this scenario, it is relevant to quantify and classify patients seen at this service.

Methods This retrospective study was developed in the SCDST ambulatory at EPM-UNIFESP in São Paulo, Brazil. Data was collected from medical records of 1908 patients seen at the service from 1999 to 2015, including sociodemographic, sexual and medical history.

Results Most of the 1908 patients were men (1413%–74%), with age between 19 and 23 years (20,8%). 792 of were single (56%) and 622 had studied up until secondary school (44%). The majority had sexual relations with women only (84,6%), while 215 (15,2%) were men who have sex with men (MSM). Sexual activities began between the age of 14 and 16 years for 620 of them (43,8%) and 885 had only one partner in the previous month (62,6%). Use of condom in every sexual activity was seen in 319 of them (22,5%), while 532 (37,6%) denied its use. The most common diagnosis among men and women was condyloma acuminatum (40,7% and 29,2%, respectively). 108 out of 120 cases of HIV seen at the service were men (90%) and 68 were MSM (63%). The vast majority of the HIV positive also presented with another STI (94,1%). Lost of follow-up was seen in 1039 patients (54,45%).

Conclusion The majority of patients were single, young men who did not practice safe sex. The most common diagnosis was condyloma acuminatum for both genders, and most of them did not receive medical discharge. HIV was more common in MSM. It is important to develop strategies to bring awareness about safe sex and the most common STIs, and improving care for these patients.