A Ag/Ag+ reference electrode in propylene carbonate (PC) was developed. Simple preparation, fast response, good stability and high reproducibility characterize it. Nernst slopes for this electrode were determined at different concentrations of supporting electrolyte. Positive deviations from the expected slope of 2.3 RT/F were found. The activity coefficient γAg+ increases with increasing concentration of supporting electrolyte, at constant silver ion concentration, in qualitative agreement with the positive deviations from the theoretical Nernst slopes. The exchange current density of Ag/Ag+ (20 mM) is 2 × 10-5 A cm-2. The effect of the addition of small amounts of water to the solvent was found to be of minor importance.