The effects of extreme cold on sensory nerves are discussed and a clinical application of these effects is proposed. The structural changes observed following the freezing of sensory nerves in the rat are described and correlated with the clinical results in patients with chronic facial pain treated by cryogenic peripheral nerve blockade. It is suggested that this technique offers features which are not shown by any other method for interrupting peripheral pain pathways and provides a useful alternative to existing methods of treatment for chronic pain.