A patient with acute secretory diarrhea refractory to conventional therapy received calcium caseinate as sole nutrient, based on the recognized development of constipation and fecaloma in patients receiving this agent. Complete remission of diarrhea followed within 10 days. An inhibition of intestinal motility mediated by B-casomorphins released after hydrolysis of casein in the intestinal tract may be the mechanism involved in this effect. These exorphins have varying effects upon the opioid receptors of the intestinal tract.