Geriatric patients tolerate hypothermia poorly. There is an age-related decline in the function of the autonomic nervous system and in the ability to increase heat production, which results in thermoregulatory impairment. The constant irrigation of cold fluid through the bladder, in addition to its intravascular absorption, can rapidly lower core body temperature. Furthermore, these patients are in cold operating rooms, and receive intravenous fluids at ambient temperature. The anesthetic technique used, general or regional, does not appear to influence intraoperative hypothermia. However, the use of warm intravenous and irrigating fluids, warming mattresses, and even warmed anesthetic gases, will help minimize the problem of excessive heat loss. Shivering, a direct consequence of hypothermia, causes increased oxygen consumption. Therefore, supplemental oxygen should be used in every patient. Shivering also increases venous pressure and promotes hemorrhage. Maintaining body temperature is an important consideration in providing for optimal care of TURP patients.