Exhibitionism was stated by East to be the commonest sexual offence for which men are received into prison; this proved to be true in 1946, when 98 men charged with exposing themselves were received into Brixton Prison during the year. Exhibitionism is customarily dealt with under Section 4 of the Vagrancy Act, 1824, and the offender is charged with being a Rogue and Vagabond in that he “did wilfully, openly, lewdly and obscenely expose his person with intent to insult a female.” The term “exposure of the person” is presumed to be synonymous with exhibition of the genitals. The 98 cases about to be discussed represented 32.2 per cent. of the sexual offences and 1.95 per cent. of all offences received into the prison during 1946. Exhibitionism presents a difficult problem both to the doctor and to the layman, as it is often apparently nonsensical and meaningless. All cases received into prison are specially interviewed as a routine and frequently the Court requests a report as to the accused's state of mind. In this series this was requested in 88 cases—a much higher proportion than for any other offence.