An atypical form of Meckel's diverticulum is presented. A 5-year-old girl was admitted with recurrent urinary tract infections. Ultrasonography showed a cystic mass, which pressed and displaced the urinary bladder on its posterosuperior aspect. Laparotomy results showed a cystic mass originating from the antimesenteric border of the ileum, which was attached tightly to the urinary bladder. It was diagnosed as a cystic Meckel's diverticulum, which had undergone abscess formation with preservation of the ileal mucosa in some areas and had severe inflammatory changes on its wall. The case is unique both in the mode of presentation and type of complication. Copyright (C) 2001 by W.B. Saunders Company.