There are controversies existing in the literature, concerning the formation of sulfoxy species (sulfates, thiosulfates, sulfites) during the oxidation of galena (lead sulfide) surface. In view of those controversies, the XPS investigations of galena oxidation with the special reference to the oxidation of sulfide sulfur were undertaken. The results of the present work show that the sulfoxy species are formed at the galena surface under favorable conditions, even in the initial stage (first few minutes) of oxidation, and can be investigated by XPS. Those sulfoxy species may be best characterized as a mixture of thiosulfate and adsorbed SOn species. However, they are easily decomposed at the presence of atmospheric carbon dioxide and in the vacuum, even at the room temperature, therefore special precautions have to be undertaken to observe their formation by XPS.