Biological properties of axerophthene, the hydrocarbon analog of retinol, were studied in vitro and in vivo. In [hamster] tracheal organ culture axerophthene reversed keratinization caused by deficiency of retinoid in the culture medium; its potency was of similar magnitude as that of retinyl acetate. Axerophthene supported growth in hamsters fed vitamin A-deficient diets although less effectively than retinyl acetate. Axerophthene was less toxic than retinyl acetate when administered repeatedly in high doses to rats. Administration of an equivalent p.o. [oral] dose of axerophthene caused less deposition of retinyl palmitate in the liver than the same dose of retinyl acetate, while a greater level of total retinoid was found in the mammary gland after administration of axerophthene. [Retinoids have been found to inhibit carcinogenesis].