THE FINDINGS of free chyle in the peritoneal cavity as the only cause for a patient's "acute abdomen" is an unusual and startling experience. Chronic chylous effusion, either into the peritoneal cavity as ascites or into the chest as chylothorax, is a not infrequent clinical phenomenon and is usually accompanied by little or no acute discomfort to the patient. Acute chylous peritonitis, on the other hand, results from the sudden outpouring of chylous fluid into the free peritoneal cavity, from any of a number of causes, and produces all the signs and symptoms suggestive of an acute abdominal catastrophe. Just as chronic chylous ascites and chylothorax are not disease entities, but rather symptoms of another underlying process, so too, acute chylous peritonitis is a clinical and pathophysiologic manifestation of an underlying disease process. This acute process, dramatic and emergent when it appears, is seldom recognized. Renner, in 1910, described the