The activities of 39 single cells, located in the ventroposterior nucleus of the rat thalamus, were recorded from rats deeply anaesthetized with xylazine and ketamine. The activity of each neurone was recorded before and during noxious tail heating. In all, 17 neurones were excited, 11 were inhibited, and 11 were not affected by the noxious stimulation. The possible function of each type of response in the coding of nociceptive information is discussed.