It was hypothesized that antisocial behavior and deviant peer involvement assessed prior to puberty, at grade four, would predict initiation of sexual intercourse by grade nine. The hypotheses were tested on a sample of 201 boys who were at risk for delinquency. The subjects participated in an extensive multiple method/agent assessment for both parents and the boy including interviews, home observations, questionnaires, test data, telephone interviews, school questionnaires and records, and court data. The multiple regression analysis showed that deviant peer association and antisocial behavior along with anxiety, assessed at grade four, and pubertal maturation assessed at grade 6, were significant predictors of initiation of sexual intercourse by grade nine. The results revealed that characteristics of the boy at grade four were more powerfully predictive of initiation of sexual intercourse by grade nine than were the family management constructs of supervision and discipline. The process was hypothesized to progress from poor family management to antisocial child behavior, involvement with a deviant peer group, and early sexual intercourse. (NB)