Labelling theorists have stressed the importance of the first conviction in court as a significant change in an individual's public identity. Being described as a ‘murderer’, ‘thief’, etc. may have different implications for the development of a deviant identity. This paper describes the crime profile of offenders at the defining moment of their first criminal conviction. Using the six birth cohorts derived from the Offenders Index, changes over time are considered in two ways: changes within a birth cohort and changes between birth cohorts. There are considerable changes in the patterns of offending over time, with important gender differences. Three offence categories of burglary, robbery and violence, and drugs are considered in detail. Burglary has an age effect over time. Robbery and violence seem to have a significant cohort effect, while drugs offences show some evidence of a period effect.