The aim of this study is to describe some characteristics of the sexual behavior of adolescents in Spain and to compare these characteristics according to gender, using a cross-sectional survey. Participants were 1.279 male and female adolescents who reported having had sexual intercourse. A questionnaire about sexual behavior was applied at their high schools and during school hours. Data were collected between 2006 and 2007. Mean age at the onset of sexual intercourse was 14.8 years in males and 15.0 years in females. Males and females were different according to the type of partner at the last sexual intercourse: 63.0% of males had a steady partner compared to 90.5% of females (p<0.01). The mean number of sexual partners during the last 12 months was higher in males than in females (M = 2.1 and M = 1.5 partners, for males and females, respectively, p<0.01). 50.0% of males had sexual intercourse under the effects of drugs versus 39.3% of females (p<0.01). STD and HIV prevention programs should be designed considering the differences according to adolescents’ sex.
