The effects of early postoperative nasoduodenal feeding on nutrition and metabolic response were studied using 24 patients after biliary surgery. The patients were randomly divided into two groups with 12 in each group. Group I was fed via a nasoduodenal tube from the first postoperative day but control group II was not fed until the fourth postoperative day. The hospital blenderized tube feeding diet provided the enteric nutrition (17% protein, 33% fat and 50% carbohydrate). The nutritional status of the 2 groups was compared over a one week period. The changes in nitrogen balance were measured daily for 8 days. The group fed early had a significantly reduced negative nitrogen balance when compared to the group whose feeding was started later. (-1.91 +/- 1.05 g/day vs -5.84 +/- 0.48 g/day). There was no difference in serum albumin and transferrin levels, but serum prealbumin levels in the group fed early were more desirable than those of the control group (from 15.8 +/- 2.5 mg/dl to 28.9 +/- 3.8 mg/dl vs from 18.0 +/- 2.0 mg/dl to 25.9 +/- 3.9 mg/dl). Total lymphocyte count was also better in the group fed early than in the controls (from 1,325 +/- 204 cells/mm3 to 2,655 +/- 584 cells/mm3 vs from 1,277 +/- 188 cells/mm3 to 1,877 +/- 440 cells/mm3). All the patients in group I felt better than those in group II during the study course. These results indicated that those patients provided with early nasoduodenal feeding after a biliary operation displayed a better nitrogen balance, and a faster increase in short half life visceral protein and total lymphocyte count.