The aim of this study was to explain the masturbation frequency and sexual relationships in adolescents based on age, religious adherence, erotophilia, attitudes toward sexual fantasies and masturbation, and the traditional sexual double standard. A sample of 1120 Peruvian adolescents aged 13–17 years responded to a socio-demographic questionnaire and different scales about sexuality. The frequency of masturbation and sexual relationships, as well as in the sexual attitudes evaluated differed by sex, with boys scoring higher. The masturbation frequency was explained by erotophilia in boys, and by positive attitudes toward sexual fantasies in both sexes. The frequency of sexual relationships was explained by age and positive attitudes toward sexual fantasies in boys and only by the latter in girls. Positive attitudes toward sexual fantasies stand out as a variable for understanding sexual activity in adolescents.
