The absolute half-cell entropy is defined here as the entropy of the process M-->M+ (solution)+e-(gas). A method of determining absolute half-cell entropies is described. The relationship is discussed for single-ion entropies in solution. ∆S0 for the hydrogen electrode is provisionally recommended to be -67.5+/-1.4 J/K mole at 298 K, based on a previously recommended value for the absolute entropy of H+ in water. More accurate measurements should be attempted.