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, comprising: infrared radiant heating means which in use is located in an unobtrusive position near the patient to provide radiant heat to the entire body or one or more parts of the body of the patient; and control means in communication with the heating means for controlling the intensity level and distribution of intensity of the radiant heat on the patient's body such that in use 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.