A treatment of cancer by the application of chemical reactions intracellularly capable of the intracellular generation of heat so as to induce selective thermal death of cancer cells in living tissue. Metabolizable minute particles of a size less than one micron are intravenously injected into the patient and absorbed by the cancer cells. The oxygen level of the patient's blood is then increased. The rate of intracellular chemical reaction in the cancer cells due at least in part to the intracellular presence of these minute particles is thereby increased and intracellular heat generated. The oxygen level is increased until the intracellular temperature has increased at least 8.0 degrees Centigrade but not more than 9.5 degrees Centigrade thereby selectively killing the cancer cells without damaging the normal cells.