A formula of temperature homeostasis of the body during inoculated tumor development was described. The basic data were temperature parameters of tumor S-45 inoculated to 180 rats subcutaneously and intramuscularly. Thermography was used as a method of investigation. An analysis of the results obtained led to a conclusion of a principal difference in the nature of heat processes in the body with tumors at different depths. In addition to it, the heat status of a tumor reflected the state of the vascular system making it possible to assess a necessary degree and nature of therapeutic exposure. Taking into account two periods of a heat status of the body one could choose the most effective therapeutic method during tumor development. The above material formed the basis for producing a heat model of tumor in order to improve methods of cancer diagnosis and therapy.