Both patients were acutely ill, and minimized their histories of passing large amounts of mucus from the rectum. The first patient died unexpectedly, but the second responded to therapy, once the correct diagnosis was made. Analysis of the rectal discharge of the second patient on several occasions demonstrated large quantities of potassium, sodium, and chloride. Loss of potassium was especially severe. Indirect evidence, including electrocardiograms, suggested that hypokalemia was present, even when levels of serum potassium were normal. This condition may cause unexplained morbidity and sudden mortality, unless the histories of such acutely ill patients with seemingly mild intestinal symptoms are carefully evaluated and sigmoidoscopy is performed.