Abstract: A method and apparatus for heating the interior surfaces of a hollow organ or orifice of the human body for the treatment of viral infections, microbial infections, and cancers, the apparatus including an insertion body 11 having a semi-rigid support tube 12 and an inflatable balloon 17. Conduits 38 and 39 connect the interior of the inflatable balloon 17 with a heating and pumping unit 31 for heating liquid and circulating liquid within the inflatable balloon to heat the outer surface of the inflatable balloon. For treating infections and cancers, the insertion body is inserted into the organ or orifice and inflated and heated to a selected temperature, e.g., 44.degree. C., and maintained at the temperature for an extended length of time, e.g., for four hours.