The true incidence and prevalence of sexual abuse against children is difficult to ascertain. Differing sampling methods, definitions of sexual abuse and methods of information-gathering have a significant effect on the rates reported. General population studies (Morrison et al, 1994) in the USA and Europe reveal a rate between 0.7 and 1.83 per 1000 children. Data from prevalence studies (Morrison et al, 1994) highlight large differences, with rates varying from 7 to 62%; meanwhile, only between 2 and 17% of sexual assaults are reported to the police. Many of the reported offenders are not prosecuted because of difficulties with the child's statement. Some offenders are cautioned, others are charged with specimen charges or have their charges downgraded. Despite an increase in the reporting of sexual offences since the 1970s, they account for only approximately 3% of all offenders on probation and 8% of male offenders in prison even though the number and length of prison sentences for sex offenders has increased since the 1970s. Convicted female offenders remain a very small group with only 23 convicted female sex offenders in custody in 1989.