A process for removing sulfur compounds, particularly hydrogen sulfide, from a waste gas wherein sulfur dioxide is introduced into the process gas at multiple process locations. Quantities of sulfur dioxide are introduced into the process gas stream at one or more locations preceding catalytic reaction. The process of the present invention may be practiced for Claus processes involving initial thermal reactions, and may be practiced without necessity of preliminary thermal reaction. In an embodiment of the invention, one of the injection locations of sulfur dioxide is the thermal reactor.