Alkyl aryl ethers are oxidized in acetonitrile in two very closely spaced waves. A detailed investigation has been carried out in the case of p-methoxytoluene, using both voltammetry and preparative electrolysis. The kinetics of the first anodic peak correspond to a second order rate law, both in anhydrous medium, and in the presence of water. On the preparative scale, the controlled potential electrolysis at a potential located on the first wave gives different products depending on the operating conditions. When small amounts of water were present, two new compounds were obtained as the major products: a 2,5-cyclohexadienone substituted in the 4 position by the starting compound, and the phenol resulting from an acid catalyzed rearrangement of this cyclohexadienone. A mechanism accounting for the nature of the reaction products in wet acetonitrile is proposed on the basis of the voltammetric and coulometric data as well as of the result of the electrolysis performed in the presence of O-18 labeled water.