After the rapid development of microwave power generating devices during World War II for military purposes, many practical uses of microwave power were identified. One of the early applications in medicine was the use of microwave heating, or “diathermy,” to warm tissues for therapeutic benefits [Moor, 1965; Schwan, 1965]. It is still believed that increased localized tissue temperature promotes blood flow and healing, relieves pain, and there is some biochemical basis for this presumption. A more recent medical application of microwave power has been to generate local tissue hyperthermia, or temperature elevation, as a possible cancer therapy. It has long been reported in the literature that temperature elevation retards cancer growth. Recent studies have indicated that heat may preferentially kill cancer cells in comparison with normal cells, and it has also been demonstrated that local hyperthermia can make radiation therapy and chemotherapy more effective [Proceedings, 1975].