Realistic three-dimensional models that predict temperature distributions with a high degree of spatial resolution in bodies exposed to electromagnetic (EM) fields are required in the application of hyperthermia for cancer treatment. To ascertain the thermophysiologic response of humans during hyperthermia, a finite-difference procedure for calculating both the EM deposition and heat transfer within the body has been developed. This model possesses sufficient spatial resolution to consider basic anatomical features including organs and tumors. The flow of heat into and out of the body has been simulated; this includes internal heat generation (metabolism and EM deposition), cooling and distribution of heat by blood flow, thermal conduction throughout the body, evaporative heat loss, and radiation and convection from the outer surface of the body to the environment. Dynamic thermoregulatory behavior such as peripheral vasomotor responses (skin vasodilation and vasoconstriction) and variable sweating rates were also simulated. Two hyperthermia scenarios were studied with the model.