The promise of hyperthermia has yet to be realized, but the fundamental idea and the effects of heat on (cancer) cells are well known. Cell death from exposure to heat is a function of both the intensity of the heat and the length of the exposure. Cells die by necrosis and by apoptosis. Sublethal heat doses sensitize cancer cells to radiation and drugs. Because of advances in chemistry and physics, harnessing the power of heat to kill cancer cells seems achievable now! Using novel systems embodied in the combination of molecular-targeted nanoparticles and hysteretic heating of the nanoparticles with "focused" alternating magnetic frequencies (AMFs), heat delivery can be better controlled. Importantly, hyperthermia does not damage, and may actually enhance, the immune system. Trials in patients are needed to settle the clinical role of new thermal treatment.