To study the effect of jejunal feeding on gastric pH, 13 multiply injured trauma patients having needle catheter jejunostomies were prospectively evaluated. Normal saline and one-half strength Traumacal were infused alternately at 50 cc/hr for 24 hours and gastric pH was measured every other hour. If gastric pH dropped to 4.5 or below, patients received 30 cc of antacid via nasogastric tube. A total of 324 gastric pH determinations were made and 93 doses of antacids were administered. Average gastric pH during Traumacal infusion was 5.34 and did not significantly differ from the average pH (5.37) during saline infusion. Using multivariate analysis to control for antacids, along with diurnal and day-to-day variations, no statistically significant effect of jejunal feeding on gastric pH could be demonstrated. These results suggest that prophylaxis for stress ulceration needs to be maintained in severely injured patients fed via the jejunum.