Six cases of avulsion injury to the pelvi-ureteric junction due to blunt abdominal trauma are reported. Primary repair was done in three cases and nephrectomy in the rest. The special problems in the diagnosis and treatment are discussed. Pelvi-ureteric junction rupture due to blunt external trauma is a distinct clinical entity. The early diagnosis of the injury is rendered difficult by the paucity of early clinical signs and symptoms. A high index of clinical suspicion and early intravenous pyelography in suspected cases will improve the percentage of cases diagnosed. The treatment of choice is primary repair by ureteropelvic anastomosis. In selected cases where primary anastomosis is not possible procedures such as ureterocalycostomy or the use of an ileal segment may be feasible. As the injury commonly occurs in young children, renal preservation is of paramount importance and nephrectomy should be performed only as a last resort.