Embryonic retina is one of the possible cell sources that will repair degenerated retina such as retinitis pigmentosa. Retinal progenitor cells isolated from embryonic rats could be cultured and expanded in serum free medium with both epidermal growth factor and basic fibroblast growth factor. We analyzed the properties of two different retinal progenitor cells in terms of culture periods. Retinal progenitor cells from embryonic retina could be expanded keeping immature cell properties and had the ability to migrate into degenerated adult retina from subretinal space after transplantation. They differentiated into neurons and glias, even into photoreceptor cells both in vitro and in vivo. However, they appeared to lose their tissue specificity after a long-term culture.