A semiparametric group-model is used to cluster 854 individuals into groups with similar developmental trajectories. The most important findings of the study relate to the substantial group of adult-onset offenders (40 percent) and a group without any previous criminal records (19 percent), next to a group of early starters (11 percent) and a group of persisters (30 percent). Up to date, no trajectory study has discovered such a vast share of adult-onset offenders. Furthermore, the findings turn out to be quite robust, if trajectory analyses are applied to different kinds of criminal activities and to different roles in criminal groups. Tables, figure, references, and appendix (Published Abstract)