Abstract A single-unit study was undertaken in the squirrel monkey to characterize the response of units in the cerebral cortex to temperature stimulation of the skin. Thermal stimulation was applied to the hand with a Peltier module. Thirty-one thermally responsive units were found in both the precentral and postcentral gyri. Individual units were found to respond to either steady-state temperature levels or to phasic temperature changes but never to both. Responses to steady-state thermal stimuli were characterized by monotonic increasing thermometer functions or decreasing thermometer functions. Responses appearing to signal deviation from steady-state neutral temperature without changes in mean frequency of firing were also observed. Responses to phasic temperature changes were increases or decreases in frequency of discharge to both warming and cooling, or were similar to the phasic behavior of ‘cold’ units. All but 3 of the 15 units tested for a tactile receptive field responded to mechanical as well as thermal stimulation.