A criminal career is the longitudinal sequence of crimes committed by an individual offender. The criminal career approach partitions the aggregate rate of offending into two primary components: participation and frequency. Research on criminal careers has generated a wealth of information regarding the longitudinal patterning of criminal activity. A review is conducted of studies that have served as platforms for criminal career research and findings of some of the major cohort and longitudinal studies. There is a brief review of the criminal career report published by the National Academy of Sciences (NAS) in 1986. Theoretical challenges and developments since this report are identified and newly articulated criminal career features are discussed. Methodological issues are outlined that arise in criminal career research including issues relating to data, research designs, analytic techniques, and general analytic issues. An overview is provided of the empirical findings generated by criminal careers research, with a concentration on the dimensions of criminal careers. There is a discussion of selected policy implications including the identification of career criminals and policies associated with sentence duration. An agenda for future theoretical, empirical, and methodological research is offered. The criminal career paradigm was developed to structure and organize knowledge about features and dimensions of individual offending and the patterning of criminal activity over the life course. Important evidence has been provided on criminal career dimensions, between- and within-individual hypotheses regarding the causes and patterning of criminal activity, and methodological and statistical techniques that furthered the study of criminal careers. There has also been evidence regarding the within-individual patterns of criminal activity that underlie the aggregate age/crime curve that challenges claims that the shape of the aggregate age/crime curve is the same for all offenders and is unaffected by life events after childhood. Information derived from criminal career research is important to advance fundamental knowledge about offending and to assist criminal justice decisionmakers in dealing with offenders. 6 tables, 412 references