Abstract: A thermotherapeutic apparatus comprises an internal applicator adapted to be inserted into a body cavity of a patient. The internal applicator includes an electrode for warming the tissues of the patient's body with use of an applied voltage, a holding member for holding the electrode, a balloon surrounding the electrode and attached to the holding member, a feed/discharge unit for feeding into and discharging a fluid from the balloon, and a mechanism for situating a radiation source, used in radiotherapy on the body tissues, in the vicinity of the electrode.