AbstractIt is known that dichloroethylamines in which the two chloroethyl groups are bound to different N atoms at a given distance from each other retain their activity and considerably lower their toxicity. It was assumed that by controlling the distance between the two chloroethyl substituents to the polymer chain a product of analogous action could be obtained. Two possibilities of binding monochloroethylamine (MCA) to a polymer were investigated: (1) Copolymerization ofN‐vinyl pyrrolidone (VP) with monochloroethylamide of methacrylic acid (MCAMA). The constants of copolymerization of this pair:r1= 3.88 ± 0.31 andr2= 0.089 ± 0.017 were determined, as well as the mean length of the elementary link of the copolymer chain. It was found that at a ratio of VP:MCAMA = 1:3 a copolymer of statistically probable structure could be obtained in which the distance between two monochloroethylamine groups is the most appropriate: about 6 atoms. (2) A polymer‐analogous reaction of the copolymer of VP with maleic anhydride (MA) permitting the binding of MCA to the polymer chain by severing the MA ring. It was established that the reaction proceeded best in a medium of dimethylformamide at 80°C for 1 hr. Water‐soluble products characterized by their C1 content and ir spectra were obtained. These products showed a physiological