The cathodic reduction of hydrogen chloride dissolved in LiCl-KCl eutectic has been studied by both chronopotentiometry and linear sweep voltammetry using a platinum electrode. The reduction reaction has been found to proceed by a reversible one-electron transfer process forming a soluble product. ��� Diffusion coefficients calculated from solubility measurements and the electrochemical studies are considerably higher (e.g. 2.1 x 10-4 cm2 s-1 at 793 K) than most other solutes in molten salts but in good agreement with results from a less detailed study. The high value is probably due to the small ionic radius of the proton as compared to other ions in the lattice of the molten salt system.