Coprecipitated catalysts (70-x)NiO-xMgO-30Al(2)O(3) (x = 0(10)50%), were calcined at 400degreesC and reduced with H-2 at 20-800degreesC and 3 h/800degreesC, NiO reduction degree 97-100%, specific (active) surface 61.5-95.4 (8.4-32.3) m(2)/g, surface acid strength 0.78-1.0, Ni crystallites 6.1-27.3 nm. As xMgO was increased, temperatures had to be raised from 700 to 864degreesC to reduce NiO. At x = 10%, the active (Ni) surface was 32.3 vs. the 10.4 at x = 0%. Steam reforming of methane was run at H2O/C = 1-6 over 150-950degreesC. With 4 vol% of H-2 and H2O/C = 3, the 10% MgO catalyst activity fell and then leveled off through to 50% MgO. Coke buildup curves followed typical courses. Coke resistance, highest at x = 30-40%, was superior to that of Ni/Al2O3 catalysts.