Sclerosing encapsulating peritonitis is an uncommon but potentially lethal condition, which can lead to severe complications such as bowel obstruction, enterocutaneous fistualas and necrosis. The treatment is debated because of the high morbidity and mortality of the surgical approach. The aim of this study was to contribute to achieving a better approach to surgical treatment of sclerosing encapsulating peritonitis. This report describes an even rarer case of idiopathic sclerosing encapsulating peritonitis diagnosed intraoperatively, observed in the Insubria University Department of Surgery in Varese, Italy, where surgery was mandatory due to the sudden onset of the disease and lack of a definitive diagnosis. Temporary ileostomy and partial resection of the peritoneum were performed. At present (December 2002) the patient is alive and well. Management of sclerosing encapsulating peritonitis is controversial, but the surgical treatment should be as conservative as possible. Guidelines for the treatment of sclerosing encapsulating peritonitis are needed.