The adsorption of dopamine (DA) on gold electrodes in aqueous sulfuric solutions of pH = 1 has been analyzed with the aid of in situ voltammetric and ellipsometric techniques. The initial stage of the process is the formation of an approximately 50-nm thick incipient hydrous gold oxide interface on the metal. Dopamine diffused into the incipient-oxide adlayer is weakly adsorbed. Significant variations of the pseudocapacity in the 0.6 < E < 0.9 V potential region were detected as a function of the adsorption time and of the gold surface state that was obtained when cycling the potential in sulfuric or perchloric solutions. The optical index and thickness of the incipient oxide were estimated.