The densities (cells/mm2) of gastric inflammatory cells were determined. Fifty-four dyspeptic children, of whom 12 had proven Helicobacter pylori infection, were compared with 13 healthy children. The mean antral lymphocyte density for healthy children was 604 cells/mm2 (95% confidence interval [95% CI], 414-793); for plasma cells, 411 (95% CI, 274-548); for neutrophils, 0; and for eosinophils, 4 (95% CI, -4-13). H. pylori-positive children had significantly higher mean densities of all cell types: lymphocytes, 1,738 (p < 0.001); plasma cells, 1,640 (p = 0.001); neutrophils, 371 (p = 0.023); and eosinophils, 263 (p < 0.01). Successful eradication of H. pylori resulted in reduced numbers of all cells. The gastric body cell densities paralleled those of the antrum. Of the dyspeptic children negative for H. pylori, 43% had antral gastritis, 43% had body gastritis, and 29% had pangastritis, as determined morphometrically. Gastritis in these patients was defined as mononuclear cell densities > 2,016 cells/mm2 in the antrum and > 1,994 cells/mm2 in the gastric body (mean + 2 SD for controls) or the presence of neutrophils. A poor correlation was observed between routine histologic description and morphometric evaluation of gastritis in H. pylori-negative dyspeptic children. Standardized morphometric cell-density determination of gastritis may be the method of choice in evaluating chronic superficial gastritis in children.