Organometallicreagents attack the SS bonds of phosphorothionyl disulphides (V) to give high yields of the corresponding S-substituted phosphorodithioates. S-alkenyl and S-alkynyl phosphorodithioates, previously unknown, were prepared in this manner. No indication of attack at phosphorus atoms, of reduction of SS bonds, or of benzylic rearrangements of the organo- metallic reagents were observed