In this chapter, we begin by reviewing the current theory regarding developmental models of crime and delinquency, and issues of persistence and desistance from adolescence into the early adult period. We argue that whereas the influential life-course persistent versus adolescence-limited model (Moffitt, 1993) has been valuable in summarizing some important features of criminal careers, this two pathway model is not adequate to explain the heterogeneity that is being detailed in recent studies of crime trajectories into early adulthood. Evidence from our research suggests that persistence of offending into adulthood may be more common than these models predict. Further, early onset, in our data, was associated with both high- and low-level chronic offending. Several studies that employ Oregon Youth Study data are reviewed and a dynamic developmental systems approach to understanding criminal activity during the early adult years is introduced (pp. 374-388). In this model, persistence and desistance are expected to be influenced by experiences and transitions undergone from the early 20s to the early 30s with a strong emphasis on romantic partner influence.