The behavioural thermosensitivity of cat paws was examined before and/or after restricted uni- and/or bilateral lesions had been made in the spinal cord between the first and fifth cervical segments. Unilateral lesions of the lateral funiculus, which involved at least its whole width at the level of the central canal, reproducibly were found to interfere with the contralateral sensitivity for temperature increases and/or decreases. No corresponding thermosensory deficiencies were found after unilateral lesions involving the ventral spinal quadrant or the dorsal funiculus. Various bilateral and combined lesions were made, but no cat ever developed thermoanaesthesia. The bilateral lesions included bilateral transections of: the middle parts of the lateral funiculi, the dorsal halves of the lateral funiculi, the dorsal funiculi, and the ventral spinal half. Most of our knowledge about peripheral behavioural thermosensitivity after spinal cord injury is based on observations of human patients, especially after anterolateral chordotomies. The present finding of contralateral thermosensory deficiencies after lesions of the middle part of the lateral funiculus fits with some of the clinical reports. The present failure to cause thermoanaesthesia, on the other hand, is inconsistent with the theory of a single ascending spinal pathway for behavioural thermosensitivity, which has emanated mainly from the clinical observations.