To test hypotheses derived from these theories, longitudinal data from 179 boys and their parents were obtained from the Iowa Youth and Families Project (IYFP), a panel study concerned with life course trajectories of parents and their children. The IYFP sample of 451 two-parent families was recruited through a cohort of all 7th grade students in eight counties of north central Iowa who were enrolled in public or private schools during winter and spring 1989. Of the 451 families, 78 percent agreed to participate in the study. Data collection involved visits to the study families and videotapes of families engaging in structured interaction tasks. Findings largely supported the life course view. Oppositional behavior during late childhood predicted reductions in the quality of parenting and school commitment and increased affiliation with deviant peers. These changes, in turn, predicted conduct problems during early adolescence. Although there was a moderately strong bivariate correlation between childhood antisocial behavior and adolescent conduct problems, there was no longer an association between these constructs when effects of parenting, school, and peers were taken into account. Further, there was evidence that improved parenting, increased school commitment, and reduced affiliation with deviant peers lowered the probability that boys who were oppositional during childhood would graduate to delinquency and drug use during adolescence. Overall, findings suggest the correlation between childhood and adolescent deviant behavior reflects a developmental process rather than a latent antisocial trait. Additional data on the study measures are appended. 33 references, 2 tables, and 4 figures