A series of dialkyl N,N-disubstituted aminomethyl phosphonates and their partial hydrolytic products,monoesters and their sodium salts,have been prepared.Dialkyl N,N-disubstituted aminomethyl phosphonates,owing to the presence of the electronegative nitrogen atom,show P=O vibration frequency at 1245-1260 cm^-1,i.e.,about 10 cm^-1 higher than that of the corresponding dialkyl methylphosphonates.