The data which have emerged from single-unit recordings of thermally sensitive neurons in the hypothalamus are reviewed. Although these neurons may be important components in the central control of body temperature, the interpretation of the data is fraught with uncertainties. The neurons in question could be primary thermosensors or part of an integrative network. There is a notable lack of control data to show that thermosensitivity is peculiar to the hypothalamus. Examples are given to show how the single-unit recording technique can be used successfully for tracing thermal information passing centrally from the skin.