)‐N'‐nitrosocarbamoyl]aminoacidamides and esters as potential antineoplastic substances are reported. N‐[N'‐(2‐chloroethyl)‐N'‐nitrosocarbamoyl]aminoacids (with the exception of the glycine derivative) were prepared by reaction of 2‐chloroethyl isocyanate with the sodium salt of an aminoacid in a heterogenous medium followed by nitrosation with sodium nitrite under acidic conditions. Condensation