An RF capacitive heating device was constructed and its deep-heating characteristics were studied using three mini-pigs. The deep-heating ability of RF capacitive heating was found to be improved by enlarging the electrodes, driving at 8 MHz, cooling the skin under the electrodes, inserting a bolus between the body and the electrodes and considering the anatomical structure of the body. The heating characteristics obtained were as follows. When applicators were placed on both sides of the abdomen of a mini-pig, 7 mm in fat layer thickness and 23 cm in lateral chest thickness, the increase in temperature of the deep part was greater than that of the fat layer. When applicators were placed on the posterior and anterior abdomen, overheating was noted in the fat and muscle near the back. The temperature was highest in a mock tumour, made by blocking blood flow to the spleen. The bio-heat equation revealed that RF capacitive heating accompanied by surface cooling at 10 degrees C could heat the deep portion of the body to 42 degrees C without excessive heating of a 1.6 cm thick fat layer.