Abstract The literature on careers of juvenile delinquents has been divided as to whether or not career specialization occurs. It has recently been proposed that the careers of delinquents may be viewed as arising from a Markov process with the observed arrest histories the result of a series of stochastic events. This approach has considerable appeal for it provides a wealth of information about criminal behavior, including predictions concerning the length and diversification of a delinquent career, the long-run distribution of various types of crimes, the extent of specialization in delinquency, and offense switching over the course of a delinquent career. In the present paper, the career patterns for a sample of highly delinquent, incarcerated juveniles are investigated. Although some support is found for specialization in delinquent careers, especially among robbery offenders, the findings generally support situational theories of crime.