Intralabyrinthine temperature recordings were made in 32 guinea pigs while the lateral semicircular canal ampulla was being cooled by a cryoprobe maintained at either −50 C or −75 C. Comparisons were made of the morphological changes produced. When the cryoprobe was maintained at −50 C, the intralabyrinthine temperatures varied from 13 C in the lateral ampulla to 30 C at the cochlear apex. A −75 C cryoprobe produced changes from −3 C in the lateral ampulla to 27 C in the apex of the cochlea. These temperatures correlated well with the morphological findings described and suggest a critical temperature of about 16 to 19 C, below which epithelial damage occurs. A temperature depression plateau occurred within the labyrinth after two to three minutes of cryoprobe application, after which no further lowering of the temperature was obtained.