Compositions to yield solid solutions were prepared by coprecipitation and firing. Fine active clusters of nickel were obtained by reduction. Phase changes were followed by thermal analysis, X-rays, electron microscopy, surface area measurements, and reforming methane with CO2. Nickel on periclase remained active over 125 h with nearly 100% conversion. The catalysts suppressed carbon deposition which occurred only immediately upstream and downstream of the catalyst. Nickel on spinel solid solution caused the catalyst to shatter with a drastic increase in surface area due to formation of NiAl2O4. The pressure drop decreased the flow rate, making this catalyst infeasible.