A portable heating/cooling device for clinical hypo/hyperthermia with cuffs especially designed for arterial cooling/heating for raising or lowering the body temperature of a patient is operable by battery power or a wide range of available external power, and is usable in the field or in medical transport where such external power sources are not available. The small size, weight, and robust nature of the device allows it to be transported with the patient without the need for additional conveying devices.