Ulcerative colitis is one of the two common chronic inflammatory bowel diseases which affect the colon of children. The disease can occur at any time during infancy and childhood and is far commoner than Crohn's disease of the colon in children less than 6 years old. The Jewish population outside of Israel is at far greater risk of developing the condition than any other ethnic group. The reason for this is unknown. The chances of a family member developing the condition is 2-3 times as great as in the general population. The etiology of the condition remains unknown; however, recent advances in the understanding of the immune mechanisms in the bowel and circulation indicate there are major immunological differences between ulcerative colitis and Crohn's disease. Intestinal B cells secrete enormously increased amounts of IgG1 and a lesser increase in IgG3 in ulcerative colitis whereas in Crohn's disease, all IgG subclasses are increased, but especially IgG2. Failure of the gut immune system to control antigen crossing the colonic mucosa may be the basis for the condition. The disease is classified as moderate to severe two thirds of children as opposed to less than one third of adults. Diagnostic testing must include 3 stool cultures negative for bacterial and viral pathogens, 3 stools negative for amebiasis, trichuriasis and other intestinal parasites and absence of clostridium difficile and its toxin in the stool. Flexible proctosigmoidoscopy and/or colonoscopy should be done in every case with biopsies. Barium enema is contraindicated in the severely ill patient. Major improvements in medical treatment being tested involve the development of nonabsorbable corticosteroid enemas and sulfapyridene-free forms of salicylazosulfapyridene for use in enema and oral form. Surgery for ulcerative colitis has made major advances with the development of the Koch pouch (internal ileostomy) and ileoproctostomy. Both procedures although associated with relatively high complication rates, are esthetically and psychologically better than standard ileostomy because in neither procedure must the patient wear an ileostomy appliance. However these advanced surgical procedures are typically not done until adolescence is reached.