The electrochemical oxidation of glucose has been studied in phosphate buffer (pH = 7.4) on single crystal and polycrystalline gold electrodes using electrochemical techniques, ece situ NMR, in situ FTIR spectroscopy, and isotope labeling. Under these conditions, the results indicate that the rate determining step for the electro-oxidation of glucose is bond breaking between the hydrogen atom and the C-1 carbon atom. Gluconolactone appears to be an intermediate and sodium gluconate is the reaction product. First order kinetics with respect to glucose were also found. Gold would be a useful electrode for sensor applications, if the inhibition of the glucose oxidation by the adsorption of Cl- could be avoided.