The correlation between the transfer coefficient ct for the hydrogen evolution reaction with temperature T was studied at the dropping mercury electrode (DME). The transfer coefficient, corrected for the diffuse double layer, was found to be independent of temperature for LiCl and KCl as the supporting electrolytes. In the case of CsCl, a small residual dependence of cu on T is observed. This is most probably an artefact, resulting from lower reliability of the phi(2) correction owing to specific adsorption of Cs+ ions. The transfer coefficients have a slight dependence on the concentration of the electroactive species in the range of 0.3-100 mM HCl. In all cases the transfer coefficient is strictly independent of potential. In 3 mM HCl and at 25 degrees C, the transfer coefficients and half-wave potentials for LiCl, NaCl, KCl and CsCl are 0.53, 0.52, 0.52 and 0.50, and -1.574 V/SCE, -1.589 V/SCE, -1.599 V/SCE and -1.618 V/SCE respectively. Arrhenius plots, corrected for diffuse-double-layer effects, at different values of the corrected potential E - phi(2) converge at T = 0, as expected if cu is independent of temperature. The electrochemical enthalpy of activation varies from 30 to 60 kJ mol(-1) in the range of potentials where the polarographic wave is measured. High reliability of the measurements is achieved due to the excellent reproducibility and periodic renewal of the surface of the DME. At low HCl concentration (0.3-10 mM) the activation current is calculated from the mixed activation- and diffusion-controlled current over the entire polarographic wave. At higher concentrations, only data at the foot of the wave were used in order to eliminate the effect of the polarographic maxima.