Addition of Gd to CO/SiO2 Fischer-Tropsch synthesis catalysts (1) increases reducibility to Co metal, (2) decreases CH4 selectivity, (3) increases activity for CO hydrogenation based on the mass of Co, and (4) causes carbon deposition at lower temperatures when compared to the unpromoted catalyst. The intrinsic activity, based on H-2 chemisorption surface area, is the same for both unpromoted and promoted catalysts.