1,2,4-Thiadiazole-5-thione (2a) was synthesized from the corresponding 5-bromo compound. An alternative synthesis of the known 3-methyl-1,2,4-thiadiazole-5-thione is described. It was shown by i.r. spectroscopy that the parent compound and its 3-methyl derivative existed in the thione form in the solid state.Mercuric-1,2,4-thiadiazole-3-thiolate (5) was prepared by cleavage of the corresponding disulfide with mercury. The mercuric salt was converted to a stable (in solution) sodium salt, but the free thio compound was not isolable.