Background Much of the research on specialisation in offending tends to show that offending careers are marked by more versatile than specific criminal activity. One key limitation of this research has been that very few studies have used both official records and self‐reports to study the longitudinal mix of offences. Aims This study uses longitudinal data to examine the mixture of offences during mid‐adolescence and into early adulthood, a key transitionary period of the life course, using both self‐reports and official records. Method Data from 1354 serious adolescent offenders are used to study the mixture of offences over a 7‐year period. Results The results point strongly to the conclusion that generality is typical and specialisation is exceptional. Copyright © 2014 John Wiley & Sons, Ltd.