We have studied the antioxidant activity of N,3,5-trimethyl-4-nitroso-N-phenylaniline in comparison with industrial antioxidants diphenylamine and p-nitrosodiphenylamine. To evaluate the effectiveness of antioxidants were used the model systems - the solution of isopropylbenzene hydroperoxide in liquid paraffin and a film of 1,4-cis-polyisoprene rubber SKI-3. It is shown that N ,3,5-trimethyl-4-nitroso-N-fenilanilin provides less speed changes in the molecular weight of the polymer in comparison with diphenylamine and PNDFA on 63 and 22% respectively (during thermal-oxidative aging of elastomers is up to 2 hours at 100 ° C). Fixed effect is probably due to the greater stability of phenoxyl radicals of sterically hindered nitrosoaniline.