The reforming of CH4 with CO2 (dry reforming:) was studied at 800 degrees C over SiO2 and ZrO2 supported Pt-Sn catalysts. Several preparation methods were investigated. It was found that the Pt/ZrO2 catalyst had much higher activity and stability than the Pt/SiO2 catalyst due to the ability of the ZrO2 to promote CO2 dissociation. On this catalyst, the decomposition of CH4 and the dissociation of CO2 occur via two independent pathways. The longterm activity of the catalyst is dependent upon the balance between the rate of CH4 decomposition and the rate of cleaning of carbonaceous deposits. The co-impregnation of Sn and Pt on the ZrO2 results in lower activity and stability than the monometallic catalysts. Depending on the reaction conditions, disruption of the Pt-Sn alloys may occur, causing deposition of tin oxide that inhibits the role of the ZrO2. Special preparation methods can result in the controlled placement of Sn on the Pt particle, minimizing the promoter-support interaction. These catalysts exhibit higher activity and stability than the monometallic catalyst under severely deactivating conditions, 800 degrees C, and a 3:1 ratio of CH4:CO2. It is possible to deposit Sn onto Pt/ZrO2 catalysts in a manner which reduces carbon deposition without inhibiting the beneficial role of the support.