AT THE turn of the century it was well recognized that cavitation in the spinal cord occurs in association with a variety of causative agents. Schlesinger,1in his monograph, cited cavities occurring as a result of traumatic hematomyelia; softenings of inflammatory and noninflammatory origin, and cavities resulting from malformations, tumors, gliosis, and vascular changes associated with gliosis. In later years, other neurologic conditions have been shown to be associated with the clinical features of syringomyelia and the pathologic picture of cavitation. Among these disorders are the Arnold-Chiari malformation, platybasia, the Klippel-Feil syndrome, and, more recently, herniation of cervical intervertebral discs. Little has been added to the clinical picture or to the understanding and treatment of syringomyelia other than to separate the described conditions from what is called "true" syringomyelia. In this paper eight cases with necropsy are presented to demonstrate some new considerations of this disorder. THE DEVELOPMENT OF