Lens epithelial cells from rats were serially subcultured. Five distinct stages (A–E) developed, which have been classified according to morphological and cellular parameters. The proteins of these cells were analyzed by isoelectric focusing. The differences in the protein patterns ( β- and γ-region) in diploid as well as in aneuploid stages are discussed. Changes in the protein patterns of diploid stage B cells with different CPD numbers are considered as age-related effects. The occurrence of elongated cell forms and the synthesis of γ-crystallin (only in the diploid stage) favours the assumption that lens epithelial cells from the rat retain some features of their differentiation capacity in vitro.