Rats fed a tryptophan deficient diet composed of corn developed significantly more gastric erosive disease when subjected to prolonged immobilization than similarly stressed rats fed a tryptophan enriched diet. No gastric disease developed in control groups which were not immobilized. No significant correlations were found between treatment groups and levels of indoleamines in brain and gut. However, serum tryptophan was significantly lowered only in the group of stressed rats fed a tryptophan deficient diet. This report raises the possibility that people eating preponderantly a corn-based diet, deficient in tryptophan, may be at increased risk of having stress ulcer disease of the gut.