This paper describes a case-note and interview study of a cross-sectional sample comprising of 25% of all women serving a prison sentence in England and Wales. A 5% sample of the male sentenced prison population was used for comparison. Deliberate self-harm on at least one occasion was reported by 82 women (32%); 31 (12%) had harmed themselves more than once. Of the men, 297 (17%) reported self-injury, 131 (8%) on more than one occasion.