For clinical application in cases of carcinoma of the esophagus, we developed an endotract electrode ("applicator") for radiofrequency (RF) and an RF-generator (13.56 MHz) automatically controlled by a computer monitoring the temperature of the lesion. We then designed a combined therapy of hyperthermia, chemotherapy and radiotherapy (so-called hyperthermo-chemo-radiotherapy: HCR), on the basis of the additive or synergistic effects of hyperthermia combined with radiation and/or anticancer drugs. We applied this combined therapy to patients with esophageal carcinoma, using our newly developed heating system. HCR therapy was preoperatively performed on thirty-three patients with esophageal carcinoma. In the histopathological study of resected specimens, seven out of thirty-three patients (21.2%) showed markedly effective improvement, in seventeen (51.5%) the effects were moderately effective and in nine (27.3%) there were no apparent effects. The effectiveness (markedly + moderately effective/all cases) of preoperative HCR therapy was 72.7% (24/33), and significantly higher than the 50% (54/108) obtained in one hundred and eight patients who were preoperatively prescribed radiotherapy alone or in combination with chemotherapy. We then applied the combined therapy with hyperthermia to sixteen patients with unresectable esophageal carcinoma and eleven of these patients (68.8%) showed partial and moderate responses in esophagography. This combined therapy with hyperthermia is highly effective, and shows great promise for treating patients with esophageal carcinoma.