The instability of rubber and gasoline respectively make necessary the protection of these substances against oxidation. By means of oxidation‐reduction potentials, the theory of electro‐negativity and practical tests applied empirically, it has been found that the economically important antioxidants for these systems occur in the classes of aromatic phenols; substituted aromatic amines; amino phenols and amines condensated with aldehydes or ketones. Those products well established in commerce are listed.