The thermal stability of magnetron sputtering deposited Mo/SiO2 multilayered films was investigated by isothermal annealing, cross-sectional high resolution electron microscopy and Auger electron spectroscopy. No observable structural variation was visualized at the interface between Mo and SiO2 after annealing at 400 degreesC for 2 h. At 600 degreesC, a small amount of as-deposited amorphous Mo began to crystallize at the top surface of the sample. Further increase in the annealing temperature resulted in the formation of large Mo crystalline grains in the film and destruction of the periodically distributed Mo/SiO2 multilayer structure.