Abstract: 4-Alkylthiosemicarbazides of the formulaAlkyl--NH--CS--NH--NH.sub.2are produced by heating at about 40 to 90.degree. C the novel hydrazinium salts of N-alkyldithiocarbamic acids of the formulaAlkyl--NH--CS--S.sup.- + NH.sub.3 --NH.sub.2in a solvent while removing by-product H.sub.2 S as by use of vacuum or passage of an inert gas through the reaction mixture, advantageously in the presence of a catalytic amount of sulfur to speed up the reaction. Hydrazine hydrate may also be present. The hydrazinium salt starting material can be prepared by reacting the corresponding alkylamine, ammonia, carbon disulfide and hydrazine, and the reaction solution directly employed in the heating step of the present invention without isolation of the intermediate.