Anesthesia dolorosa has been considered an infrequent complication of spinal posterior rhizotomy. We reviewed the data of all patients who underwent rhizotomy between 1962 and 1972 (15 cases). Thirteen were affected by cancer and 2 by non-neoplastic conditions. Eight developed a typical deafferentation pain (i.e., anesthesia dolorosa) (53%) while 3 who were found to have a brain (frontal 2; parietal 1) metastasis did not. Anesthesia dolorosa developed 1.5-8 months after rhizotomy. We conclude that anesthesia dolorosa following rhizotomy is more frequent than usually stated and that rhizotomy should be restricted to patients with a less than 3-month life expectancy.