Considering that scientific articles have emphasized the link between the onset of sexual life and peer pressure, the aim of this study was to identify peer pressure in the adolescents' sexual initiation from the point of view of their relationship with the group of friends. A cross-sectional study was conducted among 363 15-19 year-old teens that represented a sample ofthe adolescents enrolled in a family health unit in Sao Paulo City, Brazil. Results showed a relation between sexual initiation and age, being involved in physical experience with someone without wishing, having the majority of friends with sexual experience and dating. Eventually, data show that peers might play some influence on adolescents' option for sexual debut.