The US Department of Energy's, Morgantown Energy Technology Center (METC) has studied the use of surface acoustic waves (SAWs) in instrumentation systems that monitor deposition level and rate of change in high-temperature, corrosive-atmosphere coal conversion and utilization systems. Such deposition monitoring systems are needed to design and maintain efficient coal conversion systems. This report reviews the development of the deposition sensor and the associated testing system from the first intrusively designed rectangular, stainless steel sensor to the current cylindrical, glass-ceramic, nonintrusively designed sensor. Tests in a laboratory deposition facility have shown that the latter design, after proper calibration, is capable of monitoring deposition up to the design maximum of 3.10 x 10/sup 5/ mg/m/sup 2/ (200 mg/in./sup 2/) at room temperature. Changes from this calibration occur at higher temperatures. Tests at temperatures under 100/sup 0/F above room temperature indicate that further work is needed to permit use of this deposition monitoring technique at elevated temperatures.