Both the stereotypes held by investigating officers and the clinical literature assume that child molesters have distinct characteristics. these are generally expected to be reflected in a prior offence history of assaults on children and sexually deviant behaviour. A further assumption is that there is an escalation of offending, less serious crimes being precursors to more serious ones. To test these assumptions the criminal convictions, if any, prior to the offence were examined for all 416 detected offenders who had committed sexual offences upon children aged between 5 and 12 years, in the Lancashire Police area, during 1987, 1988 and 1989. Of the 183 (44%) of offenders who had previous convictions, 72 involved indecency, 17% of the total sample. Only 9 (2%) of offenders had an exclusive conviction history in respect of indecency. Previous convictions for theft, burglary and violence were all much more frequent. The results also do not generally support the hypothesis that serious offenders have progressed from less serious offences against children. A criminal opportunist model is proposed as of more value for guiding investigations than the existing stereotypes.