A study of the effects of synthetic analogs of dermorphin which are prime agonists of the mu-opiate receptors, on cell division in the corneal and lingual epithelium of albino rats showed that both analogs depressed DNA synthesis in the corneal and lingual epithelium 4 h after administration. In the lingual epithelium DNA synthesis and the mitogenic index were still depressed 24 h after drug administration. In the cornea cell division parameters had normalized by this time.