&NA;Preoperative hyperthermochemoradiotherapy (HCR therapy), consists of a combination of hyperthermia at 42 to 45°C for 40 minutes (2 times per week for two weeks), 5‐fluorouracil (5‐FU) intravenously (total, 1000 to 1750 mg), and a total of 30 Gy irradiation. The therapy was prescribed preoperatively most recently for 11 patients with rectal cancer. The authors used a radiofrequency system involving an endotract electrode with thermosensors for the hyperthermia. The effectiveness of preoperative HCR therapy was evaluated by irrigography, fiberscopy, and histopathologic findings in the resected specimens. Reduction in tumor size and amount was evident in all patients, with all modes of assessment. Histologically, no or only a few viable cancer cells were seen in the resected specimens in six patients, a small number of viable cancer cells in three, and a fair number of viable cancer cells in two patients; there were no complications. This method of treatment is expected to play an important role in the interdisciplinary treatment for rectal cancer.