We present four unusual colonic complications of acute lymphoblastic leukaemia which occurred during the early induction period of chemotherapy. These included a transverse colitis, a haemorrhagic proctitis, a caeco-colic intussusception and an ileo-colic intussusception complicating typhlitis. Although complications are rare, they should be considered in the differential diagnosis of abdominal pain in children undergoing chemotherapy.