The selective reduction of sulfur dioxide with carbon monoxide to elemental sulfur was studied over gamma-Al2O3 supported sulfide catalysts of Ni and LaNi with different loadings of the metals. When the feed conditions were properly optimized, about 97% conversion of sulfur dioxide and selectivity to elemental sulfur was achieved at temperatures above 400 degreesC. Parametric studies on the performance of the catalyst were conducted. The parametric studies include temperature, space velocity, and molar ratio of CO to SO2 in the feed. Catalyst samples before and after the reaction were characterized by Brunauer-Emmett-Teller measurements, X-ray powder diffraction, and X-ray photoelectron spectroscopy to relate the phase composition to the activation behavior and catalytic performance. The active phase of Ni was detected as NiS2, and the COS intermediate mechanism was proposed.