The elevated efficacy of simultaneous treatment of cancer by irradiation and hyperthermia in comparison with their sequential application was confirmed in the experiments with V-79 cells in vitro and transplantable melanoma B-16 and ELD solid carcinoma in vivo. Irradiation of the tumors transplanted in the calf muscle of mice was performed at the extended Bragg peak of accelerated protons, while extremities of the group of 6 animals were fixed one after another in a water bath at 42 degrees C (hyperthermia) or at 36 degrees C (irradiation at normal temperature). In another series of experiments, the tumors were heated with the microwave (2450 MHz) antennae and irradiated on the 60Co clinical machine. The tumor temperature (42-43 degrees C) was permanently measured with a sensor based on p-i-n diode. In all cases, a hyperthermic treatment lasted 1 h and started either 15 min before irradiation (simultaneous use of both modalities) or 1 h after the end of irradiation, as is usually performed at many institutions. These results, demonstrating a notably better effect of a simultaneous treatment using the cell clonogenicity, the dynamic of tumor regression and the survival of animals as endpoints, made it possible to initiate the development and production of microwave antennae suitable for use during tumor irradiation in clinic.