The electrochemical oxidation of glycine and lysine in strongly alkaline solution has been studied, and the nature of the adsorbed species disclosed by means of an in situ FTIR spectroscopic method. The oxidation of water was strongly suppressed by the adsorption of the amino acids and the subsequent oxidative decomposition. The adsorption of amino acid onto the electrode was achieved through the terminal COO- group of fully unprotonated anions from + 0.4 V vs. Ag/AgCl, and the concentration of the adsorbent attained the maximum at + 0.9 V. Beyond this potential, the adsorption strength was weakened, and the oxidative decomposition to CO2, NH3, acids, etc., occurred from + 1.1 V.