Background The incidence of sexually transmitted infections (STIs), particularly syphilis, is high and continues to rise among some populations, especially among men who have sex with men (MSM). Furthermore, a higher incidence of STIs has been reported in HIV-positive than in HIV-negative MSM.

Objective To determine the incidence of syphilis in a cohort of men with HIV in Buenos Aires city.

Methods Retrospective cohort study. We examined the records and visits made by men with HIV aged >18 years in our institution during a 1-year period. Venereal Disease Reference Laboratory (VDRL) results for all the men in our cohort during the study period were analysed. We considered a case of syphilis as incident if a person had a VDRL result of ≥16 DILS, provided that this was increased at least fourfold compared with a previous determination. All VDRL results ≤8 were investigated, and analysed together with the medical records, to determine if they were new cases.

Results We analysed the VDRL results and the clinical records of 1150 men followed up in our centre during the study period. Mean age was 40.9 years. According to the definition used, we registered 171 new cases of syphilis—that is, an incidence of 14.9/100 patients/year (95% CI 12.9 to 17.0). No significant differences in incidence according to age group were found, but there was a trend towards a lower incidence in older men. Ten men had two new episodes during the study.

Conclusions The incidence of syphilis in this cohort of men with HIV (predominantly MSM) was very high. In addition to maintaining high surveillance for early diagnosis and treatment, it is necessary to implement newer and more effective measures to prevent syphilis and other STIs in this population.