Little is known about the prevalence, frequency, onset, and criminal career duration of life-course-persistent offenders (LCP), compared to adolescence-limited (AL) and late-onset offenders (LO), despite the importance of these categories in criminology. This article is the first to use a systematic approach to identify the prospective longitudinal studies which could possess relevant information and to summarize the outputs of these studies. The principal investigators of these studies were also contacted to assist in identifying relevant data. Overall, 55 prospective longitudinal studies were identified; of these 14 had produced information on the prevalence of the various offending types. In seven additional studies, data was made available to explore criminal career parameters of the various offending types. The results showed that the estimates of the prevalence of LCP, AL, and LO offending varied considerably, and that few studies include criminal career duration in their definitions of LCP offenders. Surprisingly, the average ages of onset for LCP and Al offenders were similar. Much more research on LCP, AL, and LO offenders, which includes a consideration of criminal career duration, is desperately needed.