It has been established that hexamethylphosphotriamide O=P[N(CH3)(2)](3) (denoted as R) is oxidized by molecular oxygen only with the participation of initiators. Radicals attack the P-N bond, forming peroxide ROON(CH3)(2). A scheme of oxidation of hexamethylphosphotriamide by molecular oxygen is proposed. Certain properties of the peroxide are described.