Hyperthermia apparatus of HMS-020 produced by Aloka Co., Ltd. is introduced. In this system microwave energy of 2450 MHz is used to heat mainly superficial as well as intracavity cancer. The system is controlled by a microcomputer. Patient data and heating condition are inquired on a color monitor. During the heating, temperature change at monitoring points (max. 6 channels) and applied microwave power are shown on the screen. These data are stored on a floppy disc and can be plotted with 5 colors after the treatment. Temperature sensors are teflon coated copper-constantan thermocouples. The heating is accomplished with a PID control method and very stable.