Absorption studies in a 13-year-old boy after subtotal resection of the small bowel revealed, besides the well-known malabsorption of carbohydrates, fat, iron and vitamins, a decreased absorptive capacity for sodium chloride. Following the addition of 256 mM of salt to the daily diet, the stool volume almost doubled, and half the amount of the administered sodium accompanied by high amounts of potassium were excreted in the stools. The loading of control children with sodium chloride resulted in osmotic diuresis, the additional salt being excreted by the kidneys without increasing the enteral water-sodium- and potassium excretion. Since high oral intake of salt may result following subtotal resection of the small intestine in ‘osmotic diarrhea’, the oral salt intake of such patients should not be kept high. Additional salt, if required, should be administered parenterally.