The performance advantages of using silicon for actively cooled mirrors are developed through a comparison with molybdenum mirrors, the type used most extensively for high-energy CW laser applications'' In particular, maximum temperatures and distortions are related to a power loading parameter. Factors which are likely to limit the operating capabilities of both types of mirrors are considered to assess their impact on attainable performance, as compared to potential performance. Because silicOn has not been used extensively for demanding thermal structural applications, mechanical property data has been quite limited. This paper summarizes recently generated property data for single crystal. Particular emphasis was placed on short-time strength because of the paucity of such data in the literature. The test specimens used were processed in the manner expected to be employed for actual mirror components. In this way, the strength test results should represent the behavior of the brittle silicon material in its as-used form. By considering the performance potential of silicon mirrors and the properties of this material, it is possible to outline the potential advantages of such optical elements and to identify the challenges which must be met if actively cooled silicon mirrors are to become a reality.