Linoleic acid, gamma-linoleic acid and arachidonic acid are essential substrates for human nutrition. The daily requirement of linoleic acid or linoleic acid equivalent are 6.5 g/die. The recommended dietary allowance (RDA) for safety intake has been fixed to 10 g/die. During deficiency of essential fatty acids (EFA) linoleic acid concentration in tissue is diminished and the prostaglandin synthesis is lowered, too. Prostaglandins are formed exclusively from linoleic acid equivalent, mostly arachidonic acid. Augmented application of EFA lowers cholesterol and triglicerides concentration in blood. An antihypertensive effect of EFA has recently been described. Unsaturated fatty acids can be used in therapy of hypercoagulability. In the dietary treatment of diabetes mellitus EFA improve the effect of insulin. EFA stop the development of atheromatosis. Therefore one should not hesitate to practice an EFA-rich diet.