In an initial statement by Thornberry in 1987, interactional theory was presented as a theoretical explanation for delinquent behavior. Since interactional theory was first proposed, longitudinal data have increasingly pointed to the importance of extending current understanding of antisocial careers across the full life course from infancy through adulthood. This view has been heavily influenced by life course theory. Interactional theory involves understanding that the age of onset of antisocial behavior is continuously distributed across the age structure, at least through adolescence. Rather than viewing antisocial behavior as starting early or late, the data suggest such behavior starts earlier or later. Moreover, it appears desistance is also continuously distributed. While there is a clear correlation between the early onset of juvenile delinquency and career length, it is also clear these two dimensions of antisocial behavior are independent to a substantial degree. The authors conclude that the issues of continuity and change are complex and warrant further careful research. 66 references, 2 endnotes, and 3 figures