A thick/thin film sulfur dioxide sensor was constructed with a reference electrode consisting of a thick film of Ag/Li2SO4-Ag2SO4 deposited onto round discs fabricated with a solid electrolyte. Utilizing vacuum evaporation, thin films of platinum (1000 Angstrom) were deposited onto the solid electrolyte discs to form the working electrodes. Stable cell voltages were recorded for over 4 months fur air-SO2 mixtures in the range between 5.4 and 2400 ppm SO2.