Behavioral genetic research has revealed that biogenic factors play a role in the development of antisocial behaviors. Much of this research has also explicated the way in which the environment and genes may combine to create different phenotypes. The authors draw heavily from this literature and use data from the National Longitudinal Study of Adolescent Health to examine genetic and environmental effects on adolescent delinquent involvement. The results of the multivariate models reveal that genetic factors have a direct effect on youthful misconduct. Most important, however, is that genetic factors interact with delinquent peers and with low self-control to predict variation in delinquency. Analysis of the Add Health data also provide evidence suggesting that there is a shared genetic pathway to delinquent involvement, to antisocial peer group formation, and to the development of low self-control. (Contains 4 tables and 4 notes.)