The amount of immunoglobulin-containing cells in gastric mucosa from 6 patients with Ménétriér’s disease was estimated. Furthermore, the rate of gastric epithelial cell proliferation was studied in 4 of the patients. Fluorescent antisera specifically reacting with IgA, IgG and IgM were applied, and accordingly the cells were differentiated and quantitated. Other biopsies were labelled in vitro with 3H-thymidine and autoradiographs were prepared. The percentage of DNA-synthesising cells in the progenitor cell region was estimated. The number of IgM-containing cells in the gastric fundic mucosa was markedly increased, while the rate of epithelial cell proliferation was increased in 2 cases and within normal range in the remaining 2 pati