The condensation of N-(2-chloroethyl)-N-nitrosocarbamic acid 4-nitrophenyl ester (I) with sarcosinamide (II) gives the target nitrosourea. Alternatively, the nitrosation of N2-[N-(2-chloroethyl)carbamoyl]sarcosinamide (III) by means of NaNO2 and formic acid also yields the target nitrosourea.