Morphologic changes associated with rapid epithelial repair in human gastric mucosa were examined by light and transmission electron microscopy in samples obtained at biopsy. A timed series of samples covering six intervals (3–30 min) after exposure to 50% (vol/vol) ethanol was available. Samples exposed to 25% ethanol and to acidified sodium taurocholate were also studied. Changes indicative of epithelial repair were first seen in samples fixed 15 min after ethanol. In samples fixed 30 and 45 min after exposure to barrier breakers, there were widespread changes indicative of epithelial repair. We have tentatively identified three morphologically distinct types of repair: lateral movement of the epithelial cell basal plasma membrane, which maintains close contact with the basal lamina and which may occur only in the presence of continued vascular perfusion; migration of shortened, cuboidal cells with blunt pseudopods and lamellipodia. This morphology predominated over sites of vascular congestion; and the formation of epithelial arches in which the epithelial cells did not make contact with the underlying basal lamina. Rapid repair by cell migration was observed only at sites in which a grossly intact basal lamina was present.