Objective: The purpose of the study was to determine whether early postoperative enteral feeding with an immune-enhancing formula (IEF) decreases morbidity, mortality, and length of hospital stay in patients with upper gastrointestinal (GI) cancer. Summary Background Data: Early enteral feeding with an IEF has been associated with improved outcome in trauma and critical care patients. Evaluable data documenting reduced complications after major upper GI surgery for malignancy with early enteral feeding are limited. Methods: Between March 1994 and August 1996, 195 patients with a preoperative diagnosis of esophageal (n = 23), gastric (n = 75), peripancreatic (n = 86), or bile duct (n = 11) cancer underwent resection and were randomized to IEF via jejunostomy tube or control (CNTL). Tube feedings were supplemented with arginine, RNA, and omega-3 fatty acids, begun on postoperative 1, and advanced to a goal of 25 kcal/kg per day. The CNTL involved intravenous crystalloid solutions. Statistical analysis was by t test, chi square, or logistic regression. Results: Patient demographics, nutritional status, and operative factors were similar between the groups. Caloric intake was 61% and 22% of goal for the IEF and CNTL groups, respectively. The IEF group received significantly more protein, carbohydrate, lipids and immune-enhancing nutrients than did the CNTL group. There were no significant differences in the number of minor, major, or infectious wound complications between the groups. There was one bowel necrosis associated with IEF requiring reoperation. Hospital mortality was 2.5% and median length of hospital stay was 11 days, which was not different between the groups. Conclusion: Early enteral feeding with an IEF was not beneficial and should not be used in a routine fashion after surgery for upper GI malignancies.