Retinoic acid (RA) plays an important role in the development of eye and increases cell differentiation of photoreceptors in the early embryonic period. The present study aimed to investigate the effect of exogenous RA during development and morphogenesis of photoreceptors of the developing chick embryo after the initial organogeny of the retina. Fertilized eggs of Gallus domesticus were injected with a single dose of 0.5 µg, 1 µg or 2 µg of RA dissolved in 1 µl of dimethylsulphoxide (DMSO). Injections were carried out after three days of incubation. RA treatment induced cell death of some photoreceptors of the developing retina of chick embryos. Semithin sections examination revealed that the abundance of photoreceptor cells in the retinae of the treated embryos was less than that of the untreated ones. Ultrastructure examination revealed disorder in the cell organoids. Nuclear chromatin was highly condensed at the nuclear envelope. The nucleus lost its oval or spherical shape and transformed into a highly lobulated form probably in a preliminary step towards fragmentation. The results support the hypothesis that high doses of exogenous RA induce cell death and degeneration of photoreceptors during morphogenesis of the retina.