A process is provided for reducing the amount of hydrogen sulfide present in a tail gas from a sulfur recovery process. The hydrogen sulfide contaminated gas along with a gas containing free oxygen is passed through a series of hydrogen sulfide oxidation zones containing an oxidation catalyst, such as one or more oxides or salts of Ni, Co, Fe, Cu, Ag, Mn, Mo, Cr, W and V, deposited on a support, such as bauxite, activated alumina, titania and activated carbon. The initial and intermediate catalyst beds are operated adiabatically by injecting a substoichiometric amount of oxygen into the gas to be treated with respect to the amount of hydrogen sulfide present in the gas so that the temperature does not exceed 150.degree. C. The final catalyst bed is operated under conditions such that a superstoichiometric amount of oxygen is injected into the gas with respect to the hydrogen sulfide and cooling is provided so that the temperature does not exceed 150.degree. C. The invention is able to maintain an optimum selectivity toward sulfur during the catalytic oxidation of the hydrogen sulfide by controlling the temperature.