The extravasation of chyle into the peritoneal cavity is rarely associated with the sudden development of clinical signs and symptoms of peritonitis. A review of the English literature has documented 56 cases of this unusual disorder. We report a recent case at our institution, describing the pertinent clinical, laboratory, and operative findings. The chronic form of chylous ascites, usually associated with malignant obstruction of the lymphatics, does not cause this acute syndrome. With the acute form exploration is usually undertaken because of the clinical findings of peritonitis. A surgically correctable etiology is frequently found, although 55% of the cases have not been clearly associated with a causative factor. In those cases considered idiopathic, the natural history of the disease is spontaneous closure of the chyle leak with regression of the ascites.