Irradiation of 1,2,3,4-tetramethylnaphthalene (1) in methanolbenzene (1:1) or methanol-acetonitrile (1:1) under oxygen with 366nm light resulted in the formation of an epoxyalcohol (2), a diol (3), an enediol (4), and an endoperoxide (5). Based on some features of the reaction, it is assumed that this photooxygenation is due to singlet oxygen generated on excitation of the contact charge–transfer pairs of 1 with oxygen.