Early postoperative enteral nutrition has repeatedly been described in the literature but has not found its place yet in everyday clinical life. We conducted perioperative intraduodenal glucose tolerance tests in 12 patients with a healthy metabolism who had to undergo moderately severe abdominal surgery. Our results suggest that the resorption is still markedly delayed 12 h postoperatively and that the hormonal regulation is also essentially disturbed. Therefore, we believe that enteral nutrition in the early postoperative period is beneficial only more than 24 h after surgery.