During regional hyperthermia the tumor tissue is warmed up using electromagnetic wave applicators in combination with conventional chemotherapy or irradiation. The applicators induce a heating field via antennas (Fig. 1), which are mounted equidistantly in identical constructed lucite rings with variable diameters. The antennas send out radio waves that interfere in the tumor region. Regional hyperthermia is used to treat tumors of pelvis, abdomen or extremities, that had not responded to standard chemotherapy, or that had recurred after it. In children hyperthermia is possible only under intravenous sedation. The treatment takes about 90 minutes without preparation time. Chemotherapy plus hyperthermia is applied on day 1 and 4 of each treatment course. On days 2 and 3 anticancer drugs are given without regional hyperthermia.