The use of hyperthermia in cancer therapy had its origin in antiquity. Recently, some have hailed hyperthermia as the new fourth method of cancer therapy, and others have branded the treatment as "quackery" surrounded by mysticism, ignorance, and confusion. The American Cancer Society has been ambivalent, first placing it on its infamous unproven cancer therapy methods list, along with Laetril, Hoxey's cancer pills, hot water enemas, snake root oil, and other various and sundry "cancer cures." A few years ago the Society removed it from its list after deciding that hyperthermia may indeed have a place in future cancer therapy. This brief historical review highlights some of the most important early clinical discoveries and basic laboratory studies, which should help convince even the most avid skeptics of hyperthermia of the necessity of continuing the study of this most controversial form of cancer therapy.