The main emphasis of this text is on the biochemistry, metabolism and systemic mode of action of vitamin A. The physiological, biochemical and nutritional aspects of naturally occurring retinoids are clearly addressed. Chapters review biogenesis, absorption, storage, transport, and metabolic transformations of vitamin A. Further discussion includes vision and bacteriorhodopsin, vitamin A deficiency and hypervitaminosis A, and the vitamin A in prevention and cure of cancer.