Abstract: This investigation was conducted to study the metabolism of urea in growing pigs using N15-labeled urea by oral administration in conjunction with a 13.3% protein ration. Six pigs were used. During the three days on experiment, 4 pigs received different amounts of N15-labeled urea while the two control pigs received regular urea. All 6 animals were sacrificed on the 4th day. The results of the determination of N15 in both the protein and non-protein nitrogen fractions of liver, kidneys and blood plasma; muscle protein nitrogen, urine and fecal nitrogen are presented. There is a small but definite amount of the administered urea incorporated into the body protein.