Fundamental experiment of hyperthermia with excorporeal circulation for cancer therapy was made by use of heal ty dogs. As the results, the hemolysis was not found when the blood temperature of excorpoeral circulation was 45°C. Hyperthermia condition was kept enough by 42°C of circuit water and the electric blanket. It will be able to minimize the damage to the body by high temperature. The survival rate was extremely up when the value, which means the area of rectal temperature over 42°C, was under 1.0 hr·deg.