The importance of retinoic acid (RA) for the embryonic and developing systems has been under focus several years ago. The present study aimed to clarify the effect of exogenous RA during development and morphogenesis of the retinal pigment epithelial cells (RPE) 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. Exogenous Ra in different concentrations was found to affect the morphology of retinal pigment epithelial cells and produced pigment granules in some of these cells in the chick embryo during the period of morphogenesis. The results revealed that RA affected the morphological features and functions of RPE cells where the treatment with different concentrations of RA resulted in flattened cells, increasing the extracellular spaces between RPE cells, inhibiting gap junctional intercellular communication, electron dense cytoplasmic material and organelles, increasing the microvillous projections on the free surface and increasing the frequency of the pigments granules within the RPE cells with changing its localization to be on the vitread side rather than being on the sclerad and lateral sides, It was also found that RA decreased the relative volume of nuclei and increased the relative volume of the nucleoli which was observed in higher concentrations of RA. The teratogenic effect of RA on the RPE cells was limited and restricted to induction of some morphological changes. This might be interpreted as a result f deactivation of RA by the degrading enzymes which are found in the RPE cells in large amounts.