The hypothesis that a negative potassium balance decreases gastrointestinal propulsive motility by depletion of intestinal potassium has been examined. Simple dietary deficiency in rats depleted intestinal potassium but did not increase gastrointestinal propulsion. Potassium deficiency accompanied by sodium restriction diminished gastrointestinal motility as well as potassium concentration in both the small intestine and lower bowel. Administration of excess cortisone or depletion of electrolytes by intraperitoneal sucrose solution decreased propulsion without depletion of intestinal potassium, though cortisone induced severe hypokalemia. Depletion of intestinal potassium apparently is not the common factor leading to decreased propulsion even when a negative potassium balance and/or hypokalemia are present. Dehydration and sodium depletion of the small intestine generally accompanied decreased propulsion, but the significance of these changes was not obvious. The gastrointestinal tract resists potassium depletion and the mechanisms controlling electrolyte distribution in it probably differ from those in skeletal muscle.