An infrared radiant heating system for raising or maintaining a uniform core temperature of the body of a patient during surgery, substantially without affecting the temperature of the area surrounding the patient's body, includes an infrared radiant heater located near the patient to provide radiant heat to the entire body or one or more parts of the body of the patient. The system further includes a controller in communication with the heater for controlling the intensity level and distribution of intensity of the radiant heat on the patient's body such that the skin temperature of the patient's body is raised or maintained within a predetermined range resulting in the uniform core body temperature, substantially without affecting the temperature of the area surrounding the patient's body.