Primary cultures of pure bovine corneal epithelial sheets, isolated from either central or peripheral areas of the cornea and grown on an extracellular matrix, exhibited major differences in relation to their respective growth characteristics and morphology. After 15 days in culture, cells of peripheral origin covered a 40% greater area and were 2.75 times more numerous than those of central origin. Most peripheral cells were small with a polygonal morphology, whereas central cells varied considerably in both size and shape, although areas consisting of large cells were regularly observed. Differences in the rates of proliferation between central and peripheral corneal epithelial cells were maintained throughout the first and second subcultures. However, the growth rates were considerably lower in second passage cultures of both central and peripheral cells when compared with those of first passage. The growth characteristics of primary cultures of pure epithelial sheets were confirmed by further studies on corneal buttons in culture. Our results in vitro strongly support the concept of a slow but steady physiological movement of increasingly differentiated cells from the periphery of the cornea towards the centre, resulting in a constant renewal of epithelial cells in vivo. © 1989 Springer-Verlag.