We present four cases of acute mesenteric infarction in patients with active ulcerative colitis: one presenting prior to the diagnosis of ulcerative colitis, two at the time of diagnosis, and one many years after the diagnosis had been made. Intestinal ischaemia is an important part of the differential diagnosis in patients with ulcerative colitis presenting with abdominal pain. Conversely, in patients presenting with bloody diarrhoea after mesenteric ischaemia, ulcerative colitis should be considered.