Retinoic acid (RA) is known to affect developing system. The present study aimed to investigate the role of exogenous RA during morphogenesis of nervous tissue of the developing chick embryo. 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 teratogenic effects during the morphogenesis of the developing chick embryos. These effects included the axial shift of the brain structures and appearance of mesencephalon in locations where rhombencephalon and spinal cord were supposed to be. The explanation of the RA effect based on the disturbance of normal pattern of expression of genes concerned with the process of morphogenesis. In addition, RA induced the appearance of enlarged hydrocephalic heads, bilateral exophthalmos, cerebral aneurysm, congestion and extravasation. Also, RA treatment induced degenerative activities and cell death in the nervous tissues. This is explained as a result of high amounts of RA exceeding the capacity of RA degrading enzymes and thus inducing cell death and degeneration.