Diffuse sclerosing osteomyelitis of the mandible is a disease of obscure origin that may give rise to diagnostic problems. In the literature most authors suggest an infectious etiology. However, the results of treatment are generally poor. Clinical and radiographic findings in this study of 27 patients suggested an infectious origin of the disease. However, bacteriologic findings in 11 of these cases did not support this suggestion. The histologic findings showed a reactive hyperplasia of bone. The results of treatment, based on the assumption of an infectious etiology, were poor. It was concluded that the findings in this group of patients did not support an infectious etiology of the disease.