The aim of this study was to examine if biological early maturing girls and girls that percieved that boys treated them as older than they actually where drank more alcohol, were more delinquent, had more romantic relationships and sexual intercourse. Our data was collected from seven schools in Sweden. Significant relationships where found between early maturation and all four dependent variables. Significant relationships could also bee seen between how girls perceived that boys treated them and alcohol use, romantic relationships and sexual intercourse. For two of our dependent measures we found week interaction effects, for girls biological maturation and there perception of how boys treated them according to there age. Our results partly support earlier research and contribute to future research within this area.