The histopathologic changes in the ileum in postcolectomy ileitis resemble the changes that had occurred in the previously resected colon. Granulomatous postcolectomy ileitis is considered to be idiopathic. The nature of mucosal postcolectomy ileitis remains obscure, and there is sufficient uncertainty concerning its etiology to justify conservatism in surgical management. Granulomatous ileitis which does not respond to medical treatment is properly treated by resection of the involved ileum. It is reasonable to resect short segments of mucosal ileitis, but long reaches of mucosal ileitis associated with ileostomy should be managed by limited resection, construction of a proper stoma, and close postoperative observation.