Thirty-four patients with mandibular diffuse sclerosing osteomyelitis who had been treated by means of 61 decortications were evaluated retrospectively. Eighteen patients (53%) were free from symptoms on an average of 5.4 years after surgery. Of these, 12 had improved after their first operation. In the other six patients, decortication was performed two to four times before healing was clinically observable. Symptoms recurred in 75% of the cases within 12 months after surgery. Neither sex, location, extent, and chronicity of the disease nor the precise surgical technique used seemed to affect the outcome. The patients who exhibited improvement, however, were significantly older and more often edentulous than the patients in whom the symptoms recurred. Possible causes of failure were an insufficiently radical surgical procedure and retention of devitalized teeth in the decorticated area.