Abstract: An apparatus and method are provided for the selective, locally defined heating of an object, particularly a human body to destroy malignant cells of the body. A ring has a plurality of high frequency antennas or the like mounted on the inner surface thereof, capable of focusing together at a common volume. The transmitters may be mounted for limited pivotal movement, and for radial movement, with respect to the ring to provide flexibility in focusing. The ring is preferably disposed generally vertically, and is mounted so that it is rotatable about its center, and pivotal about two perpendicular axes disposed in the plane of the ring, and is mounted for reciprocal movement in a dimension perpendicular to the plane of the ring. A human body is disposed within the ring and energy is supplied to the transmitters to focus on the malignant cells of the human body, and destroy them. Various structures for enhancing the focusing effect may be provided.