Improved techniques for inducing heat: ultrasound, microwaves, diathermy with different application modalities, capable of producing localized superficial or deep, regional or total body hyperthermia have been responsible for the multiplication of clinical trials. These studies have confirmed the tumoricidal effect of hyperthermia alone, or more especially when combined with radiotherapy, and the good tolerance of normal tissues to localized temperatures of 42 to 43.5 degrees C even in previously irradiated cases. Localized heating does not seem to increase the incidence of metastasis. Enhancement ratios and therapeutic gain with respect to normal tissues are not yet well documented. Many problems, including the heterogenicity of tissues to be heated, difficulties with temperature monitoring, and selection of appropriate sequential scheduling of radiation and hyperthermia remain unsolved and further investigations are required.