The authors emphasize the study of within-individual changes in offending over time and the study of causal factors that may explain onset, escalation, de-escalation, and desistance in individual offending. In particular, they believe a better understanding of individual differences in criminal careers can help to explain why some young people become involved in delinquency only marginally and others more deeply and which groups of individuals start to desist in crime at a specific point in the life cycle. Developmental criminology is relevant to applied criminal justice for several reasons: (1) the formulation of developmental theories; (2) the study of individuals rather than variables; and (3) decisions about what behaviors to target for intervention and when to intervene. 37 references, 1 note, and 1 figure