We present results on microwave and millimeter-wave processing of materials. The research is primarily based on two systems- a 2.45 GHz, 6 kW S-band system and an 83 GHz, 15 kW gyrotron based quasi-optical system. These systems have been used for a wide range of material processing experiments. We describe the capabilities of these systems and discuss some of the results, including nanophase material production, rapid sintering, coating removal and joining of high temperature ceramics.