We compared the bovine melanotic and amelanotic retinal pigment epithelial (RPE) cells cultivated in vitro using a number of parameters. Both cell types could be readily harvested from the eye by dissection or by enzyme treatment of the RPE. Both types of cells grew equally well in the primary culture, and in serial subcultures for over 600 days, and also after being stored frozen for over two months. The two types of cells were similar in their growth patterns, morphology, chromosome characteristics and phagocytic activity but they differed in their tyrosinase activity. Although in long-term cultures cells showed chromosome loss, a high proportion of the cells retained their normal diploid chromosome number (2n = 60) with apparently normal karyotype.