By comparison with controls the investigation of 47Ca absorption and excretion kinetics after oral administration to patients with Billroth I gastrectomy (without milk intolerance) showed no differences in excretion of the isotope in urine and stool or in retention in the body. Patients with Billroth II gastrectomy had a higher degree of isotope excretion in stool and a lower retention of 47Ca. The higher absorption curves of isotope in Billroth I patients suggest a more rapid rate of 47Ca absorption without an actual change in transport capacity.