Results indicated three main reasons to include genetic factors into criminological studies: (1) the models that included genetic influence had higher levels of explanatory power than the models without genetic variables; (2) genetic factors were found to interact with environmental factors to jointly influence criminal behavior; and (3) relationships were found between parenting and delinquency, a departure from recent theoretical claims. The findings, on the other hand, were less supportive of the influence of delinquent peers, which failed to predict delinquent behavior in the current study when genetic variables were included in the models. Data were gathered from the 1979 National Longitudinal Survey of Youth (NLSY-Child), an ongoing, longitudinal, perspective study that collects information on children from before birth through young adulthood. Subjects for the current analysis were the children born to women participating in the 1979 NLSY-Child. Children in this cohort were followed up on even years beginning in 1986. The latest wave of data used in the current analysis was gathered in 1996. Variables under analysis included delinquent involvement, parent-child interaction, level of parent-child attachment, parental expectations of children, parental supervision, and delinquent peers. Random effects regression analysis and DF (formerly known as DeFries-Fulker) analysis were used to examine the data. Future research is needed to uncover the mechanisms underlying the relationships between parenting, peers, and genetic influences. Tables, appendixes, notes, references