Cesium oxythiomolybdate (Cs2MOOS3) is under consideration as a high temperature solid lubricant for silicon nitride bearings. However, CS2MOOS3 oxidizes below the proposed maximum use temperature of 800 degreesC, and the oxidation process is complex. In the presence of silicon nitride, the oxidation reactions change. The purpose of the present research was to determine the chemistry Of Cs2MOOS3 coatings grown by pulsed laser deposition (PLD) on several substrates (Si3N4, SiC, Inconel, Al2O3 and ZrO2), and to determine the changes in chemistry and crystal structure after annealing in air to temperatures up to 800 degreesC. Many of the oxidation products identified are expected to be lubricious at elevated temperatures.