Intentional injuries inflicted upon children by adults rightly cause great concern and have been studied extensively. In contrast, little is known about the pattern, nature and extent of injuries sustained by children inflicted by other children. A funded prospective study of injured children was undertaken over 18 months. Children’s injuries were studied in an epidemiologically complete population comprising the western two-thirds of Cornwall. Information was collected from ten hospitals in standardised fashion using the widely accepted Children’s Hospital Injury Reporting and Prevention Programme (CHIRPP). 597 injuries (67% involving boys) were identified as having been inflicted apparently deliberately by other children. 62% of injuries affected children aged under 12 years. 245 injuries (41%) occurred at or around school, 143 (24%) at home. Most injuries involved soft tissues, but there were 116 fractures, which accounted for 22 of the 40 hospital admissions. Interestingly, despite a description of an ‘‘assault’’, only 38% of injuries were initially coded as intentional by treating hospital staff. These results reveal the previously largely unrecognised scale of the problem of interpersonal violence between children. It is not surprising that most injuries occurred in or around school, given that this is where children interact with other children. The attitude of healthcare professionals may need to change if this problem is to be properly addressed.