The catalytic activity of 21 metal oxides in the Claus reaction and also in oxidation of H2S by oxygen has been investigated. Only part of them exhibited a stable activity. Among them, vanadium oxide was the most active catalyst in the Claus reaction as well as in total and partial oxidation of H2S. The remaining oxides were deactivated, mainly due to the interaction with H2S and conversion into sulfides. The mechanism of modified Claus reaction on the most active and stable catalysts has been studied. It was shown that the process proceeds by a concerted mechanism at the participation of both reagents on Al2O3 and TiO2 catalysts, whereas on the vanadium-containing catalyst the stepwise mechanism takes place.