This paper is limited to those catalysts and lipid oxidation inhibitors which have been found to be present either in the raw food materials or in processed food as a result of its processing. Lipoxygenase and haemoproteins are very powerful lipid oxidation catalysts in many foods. Heat treatment usually inactivates lipoxygenase but can, under certain conditions, activate haemoproteins as non-enzymatic metal catalysts. Tocopherol, normally referred to as an antioxidant, can, under certain concentration conditions, shift to pro-oxidative properties. Even volatile lipid oxidation products have been shown to accelerate lipid oxidation. Inhibitors present in raw materials are found among proteins, amino acids and plant constituents such as flavonoids. Most spices and herbs have antioxidative properties, particularly in darkness. Some microorganisms in their normal metabolism inhibit lipid oxidation or the consequences thereof. Some enzymes, especially superoxide dismutase, are claimed to inhibit lipid oxidation. Among process-induced lipid oxidation inhibitors, Maillard reaction products are those most investigated, together with protein hydrolysates. Smoking generates antioxidative compounds. In most cases the mechanism of lipid oxidation inhibition is still unknown for these materials. © 1982.