This book examines several contentious and under-studied criminal career issues using one of the world's most important longitudinal studies, the Cambridge Study in Delinquent Development (CSDD), a longitudinal study of 411 South London boys followed in criminal records to age 40. The analysis reported in the book explores issues related to prevalence, offending frequency, specialization, onset sequences, co-offending, chronicity, career length, and trajectory estimation. The results of the study are considered in the context of developmental/life-course theories, and the authors outline an agenda for criminal career research generally, and within the context of the CSDD specifically.