Fluid-filled blisters, created on the skin of the inner surface of the pinna of heparinized rats by the application of suction, showed an intact basal lamina through which protruded hairs and remnants of hair follicles. The origin of epithelial cells and their spreading over the basal lamina were studied at intervals over 36 hours using scanning and transmission electron microscopy. The majority of epidermal cells arose from the outer root sheath of hair follicles and began to spread radially before 12 hours. By 36 hours the cells were confluent over most of the blister base. Inflammatory cells were few in number and rested mainly on the bare basal lamina rather than on the resurfacing cells. Some elongated epidermal cells showing tapering foot processes appeared to be migrating in from the epidermis at the edge of the blisters. The cells spreading from hair follicles were flat and polygonal. On these sheets of cells a few small folds and many filopodia were present at intercellular junctions and at the free margin of the leading cells. Large numbers of short microvilli covered the surface of some of the epidermal cells, especially at 24 and 36 hours; other epidermal cells were relatively smooth.