The extent to which delinquents specialize in their criminal careers is unclear because of inadequacies in two related areas: the offense typologies or classifications used and the failure to consider in the analysis the entire sequence of crimes. It is argued that both of these areas can benefit from utilization of the 'career-line' metaphor from occupational literature. The arrest histories of a sample of 767 juveniles were analyzed with a technique -- variance centroid scaling -- desirable for the classification or scaling of crime. Four dimensions were discovered. An analysis of 62 careers in the sample reveals that three forms of 'developmental' careers are prevalent: careers that move (1) from burglary to serious crimes against persons, (2) from status offense to auto theft, and (3) from all crimes to drug use. The implications of these results are discussed for issues of specialization and diversity in delinquent careers and the respecification of theories and intervention strategies. (Author abstract)