Eleven gastric mucosal defects produced by endoscopic biopsy in non-tumoral areas were histologically studied in gastrectomy specimens. The biopsies had been performed from one up to seven days before the operation. The base of each defect was formed by submucosa infiltrated by erythrocytes, fibrin and neutrophils, which were later replaced by small blood vessels, fibroblasts and collagen fibrils. The mucosa of the margins bowed down towards the base of the defect. This marginal mucosa showed dedifferentiation of the glandular epithelial cells, increased mitotic index and some cystic glandular structures lined by basophilic cells. The defect was progressively covered by a layer of flattened or cuboidal cells in which no mitoses were observed; their cytoplasm contained mucosubstances similar to those of the superficial epithelium of the remaining mucosa, either foveolar- or intestinal metaplastic-type. From this layer, simple gland-like invaginations to the underlying connective tissue were observed. The findings are consistent with the regenerative events described in experimental gastric ulcers in animals. The method employed may be useful to study specific aspects on the regeneration of the human gastric mucosa.