This report describes a young woman with ulcerative colitis who developed rapidly fatal pneumococcal septicaemia. Necropsy revealed splenic atrophy. This case supports the hypothesis that splenic atrophy might contribute to the morbidity of ulcerative colitis. The occurrence of splenic atrophy in ulcerative colitis is now well established. Splenic atrophy from other causes has been associated with severe bacterial infections, often pneumococcal. It has been suggested that splenic atrophy is most severe when ulcerative colitis is active and may contribute to postoperative morbidity. This case documents overwhelming septicaemia in a patient with splenic atrophy whose colitis was in remission.