This article reports a long-term follow-up study of persons detected for a sexual offence against a child between the ages of 5 and 12. The study focuses on the likelihood of a subsequent conviction, the success (or otherwise) of risk assessment and the geographical mobility of sex offenders. It is estimated that sexual recidivists coming to the attention of the police will come from three sources: just under one third from offenders who are convicted and in high-risk categories, around one third from those who are convicted and in the more numerous low/medium-risk categories and around one third from those strongly suspected of, but not convicted for, a sexual offence.