The patterns of offending have been shifting among the 16 to 20 age group from more specialist activity to more versatile criminal behavior. It is asserted that the implications of these changes have not been fully recognized. The study heralds methodological and substantive advances. The methodological advance argues that clustering more closely represents the reality of criminal activity. The substantive change has been an overall shift from what is termed more ‘specialist’ criminal behavior to more ‘generalist’ behavior. In addition, it is estimated that the proportion of the young adult male population who are involved in highly versatile offending, characterized by at least four separate court convictions in the 5-year period, has dramatically changed. This proportion has doubled since the early 1970s. For females, age 16 to 20 years, a significant increase in versatile offending was observed, from the early 1970s to the late 1990s. The gap is narrowing between males and females; however, the difference between male and female versatile offending remains large. The study has demonstrated that changes in patterns of offending over time can most definitely be measured. The primary focus of this paper is to provide a new perspective on the offending behavior of young adults, by disentangling their patterns of court convictions over a 30-year period, and presenting such patterns in the form of underlying participation rates. It considers the convictions of 6 cohorts involving 31,456 young adults aged 16-20 from the early 1970s to the late 1990s. By this approach, the current confusion of where the problem lies in relation to young adult offenders can be avoided. Figures, tables, references, appendix