In 40 patients with insulin-dependent diabetes mellitus, the number of gastrin cells in the mucous membrane of the antrum of the stomach was measured by immunohistochemistry according to the method of L. Sternberger. The number of the cells depended on the gravity of antral gastritis, namely their number decreased as the lesion was aggravated. The basal level of serum gastrin was determined by radioimmunoassay in 144 patients with insulin-dependent diabetes mellitus. The high basal level of gastrin was recorded in patients with achlorhydria. However, no correlation was established between the gravity of antral gastritis and the basal level of serum gastrin. If the basal gastrin level is too high, the possibility of asymptomatic paresis of the stomach should be taken into account together with the other factors.