Most copper compounds increase the rate of autoxidation of rubber mixtures, i.e., they are proöxygenic agents and acclerate aging to a dangerous extent. However, copper may occur in a disguised form and have no deleterious action at all. Moreover, the effects vary considerably, even with the same copper compound, according to the composition of the rubber mixture. Thus certain ingredients, notably, tetramethylthiuram disulfide, neutralize the deleterious action of copper, whereas fat acids increase it. Nevertheless, the presence of a fat acid is not indispensable to the process of degradation brought about by copper, as is evident from tests with rubber mixtures in which the natural fat acids were previously removed from the rubber. From the practical viewpoint, protection against copper can be accomplished effectively by means of certain products such as Agerite White, BLE Powder, and disalycylalethylenediamine, all of which are excellent anticopper agents.