Extension of microelectromechanical systems (MEMS) into more extreme operating conditions will require a wider range of material properties than are currently available in conventional systems. Successful integration of new materials is dependent on concurrent development of compatible fabrication routes and scale appropriate evaluation techniques. This review focuses on emerging material classes that have potential to replace silicon-based MEMS in elevated temperature applications. Basic silicon mechanical properties and micromachining methods are reviewed to provide context for developing material systems such as silicon carbide, silicon carbonitrides, and several nickel-based alloys. Potential improvements in strength, thermal stability, and reliability are juxtaposed with fabrication, reproducibility, and economic feasibility issues that must also be addressed.