The objectives of Phase I are to test the feasibility of heating tumors selectively and perhaps noninvasively by enhancing the absorption of electromagnetic energy, and to design an experimental program which will optimize this approach to cancer treatment. The technologies of electromagnetic-absorbing materials and of hyperthermic treatment of cancers will both be utilized. Electromagnetic-absorbing materials, specifically stainless steel powders, iron compound powders and ferrites with dielectric polymer coatings, slurries, and salts in solution will be studied for their abilities to absorb electromagnetic energy as a function of frequency. Various ferroalloys, coatings and powder sizes will be considered both for electromagnetic absorptivity and for ability to be concentrated in tumors. A range of EM frequencies from about 10 kHz to 10 GHz will be considered for different tumors and will be compared with respect to practicality of application. Phase I experimentation will utilize an in vitro system to gain preliminary data regarding effective EM-absorbing material concentrations. If successful, the Phase I program will lead to an experimental program in Phase II with the potential for effectively producing deep local heating of tumors without excessive heating of surrounding tissues. Tests in Phase II can lead ultimately to an effective modality for hyperthermic treatment of cancer.