Sexually transmitted infections (STIs) should form part of the comprehensive healthcare agenda for adolescents and young people (A&Y) and testing plays a strategic role in STI prevention. However, little attention has been paid to the social and programmatic obstacles to this practice among A&Y. The aim of this study is to describe the prevalence of testing for syphilis and HIV reported by a group of A&Y, analyzing its relationship with variables potentially indicative of inequities related to vulnerability to STIs. This was a cross-sectional survey applied to students at public high schools in three cities in the state of São Paulo, Brazil. The responses of 369 young people who reported having started sexual life were analyzed. The analysis included description of the frequencies of demographic and socioeconomic variables and their associations with testing for syphilis and HIV through the chi-square test. The concentration index (CI) was also calculated, with construction of the respective concentration curve for the associated variables. Positive associations were found between occurrence of testing and living in homes with up to three inhabitants, living in a marital situation with a regular or committed partnership, previous use of primary care services and previous use of hospitals or emergency services. The concentration curve for testing STIs showed significant contributions from the associated variables. The findings indicated that situations of inequity need to be addressed in order to reduce A&Y's vulnerability to STIs.
