Experimental and clinical studies were done on intracavitary and interstitial hyperthermia with a 2 mm diameter applicator with a 7 cm tip (Aloka, Co., Ltd.). Microwave energy at 2450 MHz was used to heat tumors. An outer cannula of 16G Medicut was implanted in the tumor. When a rabbit VX-2 tumor was heated, the temperature reached over 40 degrees C at 15 watts. We applied the same method to two patients, one with recurrent oropharyngeal tumor and the other with recurrent pelvic tumor. This applicator looks promising.