The effect of rice and salty rice diets on stomach morphology was investigated in Swiss/ICR mice. Mice were fed rice, salty rice, or standard pellet diets for 3-12 months, starting when the mice were 4 weeks of age. Long-term maintenance on the rice or salty rice diet increased the dimension and wet weight of the forestomach and decreased the same parameters of the glandular stomach. Similar bidirectional changes of the forestomach (hypertrophy) and glandular stomach (atrophy) were produced by hydrocortisone treatment. Histological study showed that a reduction in the parietal cell population accounted for the regression of the glandular stomach in both cases. Evidence is presented to suggest that an excess of carbohydrate and sodium chloride combined with a deficiency of fat and protein produced steroidal disorders that in turn gave rise to hyperplasia of the forestomach and atrophy of the glandular stomach of the mice. Possible impact of the above findings on the genesis of human gastric cancer is discussed in relation to the metabolic competence of the host animals to synthesize vitamin C.