Lipoxygenases (LOX, plant LOX [EC 1.13.11.12], linoleate: oxygen oxidoreductase, animal LOXs [5-LOX, EC 1.13.11.34; 8-LOX, EC 1.13.11.40; 12-LOX, EC 1.13.11.31; 15-LOX, EC 1.13.11.33], arachidonate: oxygen oxidoreductase) belong to the family of structurally related dioxygenases containing non-heme and non-sulfide iron in the active site. LOX catalyzes the regiospecific and stereospecific insertion of molecular oxygen into the molecule of unsaturated fatty acid with the (1Z,4Z)-penta-1,4-diene structural unit in its aliphatic chain. The result of this reaction is the production of conjugated optically active (S)- or (R)-hydroperoxides of polyunsaturated fatty acids. The occurrence of LOX was determined in plants, in animals, and also in lower organisms such as mushrooms, corals and bacteria. The dominant substrate of animal LOX is arachidonic acid which is released from membrane phospholipids by phospholipase A2 or enters the cell from the extracellular space. Products of the arachidonic acid cascade can play an important role in the pathogenesis of different diseases such as asthma bronchiale, psoriasis and inflammatory diseases, cancer diseases, atherosclerosis, diabetes mellitus and renal diseases.