Abstract: The invention relates to a method of production of N,N-bis(2-chloroethyl)amino)-2-oxo-1,3,2-oxazaphosphorinane in a reaction of phosphorous oxychloride POCl3, N,N-bis(2-chloroethyl)amine, and 3-aminopropan-1-ol in a single reaction vessel, characterized by the fact that phosphorous oxychloride and N,N-bis(2-chloroethyl)amine hydrochloride are added to an inert aprotic organic solvent placed in a closed reaction vessel, in a slight molar excess in relation to phosphorous oxychloride, whereupon the mixture is cooled to temperature in the range of ?15 to ?10° C., and with the temperature maintained within this range and continuous stirring, the solution of 3-aminopropan-1-ol and the first portion of the auxiliary base is slowly added in an amount of 1 mole calculated as per 1 mole of 3-aminopropan-1-ol in an inert aprotic organic solvent, and subsequently, while maintaining the reaction mixture temperature in the range of ?7 to ?3° C.