Anaesthetic levels to cold and pinprick sensation were studied in 45 patients given continuous lumbar peridural anaesthesia by methods previously described. Anaesthesia to cold preceded pinprick anaesthesia and the level of the former rose faster for the first 5 minutes, after which pinprick anaesthesia closely approximated it. After 30 minutes the average difference was only one-half dermatone. We conclude that there is no significant zone of differential sensory anaesthesia during peridural anaesthesia as occurs during spinal anaesthesia.