Abstract: An electrode structure for use in emitting electromagnetic radiation for localized heating of tissue in medical therapy and capable of permitting deep heat penetration while skin surfaces and subcutaneous tissue remain at lower and physiologic temperatures not harmful to living tissue. An electrode structure having a wall with an emitting surface adapted to be placed in direct facial contact or in close proximity with external skin surfaces, the wall forming part of a cooling chamber through which cooling fluid is circulated to maintain the wall and adjacent tissue at selected relatively cool temperature. The electrode wall is connected to a radio frequency generator through impedance matching circuitry. In one embodiment, the wall surface is suitably curved for direct uniform contact with the surface configuration of the body to which it is applied.