Five subjects with spinal cord transections and one subject unconscious from a head injury have been studied when the deep tissue temperature (;central' temperature) was artificially lowered but normally innervated skin was kept warm, usually 34-36 degrees C.2. Shivering and/or increased metabolism was evoked when the central temperature was 34.9-37 degrees C.3. These observations are compatible with the view that there is a central receptor which can cause shivering when stimulated by a fall in central temperature.