Novel, heterocyclic derivatives of trithiophosphoric acid have been achieved through phosphorylation of quaternary salts of N-heterocycles with phosphorus trichloride, the iminohalophosphines, thus obtained in situ were subjected to nucleophilicsubstitution with mercaptans in organic solvents in the presence of HCl acceptors, preferably triethylamine. Synthesized derivatives exhibited potential insecticidal