<正> The electrochemistry of polyaniline synthesized electrochemically in acidic solution under light irradiation has been studied as a function of the applied potentials, the concentration and acidity of electrolyte as well as pH at applied potentials in the rang+0.40 to-0.5V vs. SCE. It is concluded that under selected experimental conditions the reduced repeat groups in polyaniline are oxidized by air in the dark and that this oxidation process can be strongly photocatalyzed.