Vitamin E is the term to identify a group of eight plant-derived and fat-soluble molecules with antioxidant and gene regulation functions. The most relevant form for human nutrition and health is α-tocopherol, the functions of which have been demonstrated in humans and animal models of vitamin E deficiency to be essential for homeostatic processes primarily of the central nervous system and possibly of other tissues/systems, such as red blood cells, the immune system, and the liver. The molecular mechanisms behind vitamin E’s essential role remains elusive. It is apparent however that α-tocopherol affects structural and metabolic aspects of the cellular membrane and possibly of other subcellular structures, such as the transport of vesicles and lipid droplets. Its activity as an H atom donor influences at the same time the metabolism and molecular integrity of membrane phospholipids, affecting enzymatic and spontaneous (free radical-dependent) oxidations of polyunsaturated lipids to form eicosanoids and lipid by-products, many of which are potent mediators of immunovascular processes and/or toxic molecules. Nonalpha forms of vitamin E have tissue levels, distribution and functions alternative to α-tocopherol that are regulated at different levels of liver and peripheral tissue metabolism (discussed in the accompanying Chapter 24).