This report is based on a study of the first 100 cases of protrusion of one or more intervertebral disks in which patients were operated on at the Mayo Clinic. The purpose of the study was to survey this group of cases from a neurologic standpoint and to attempt to clarify, if possible, certain features of the problem of protruded disks. A complete review of the already voluminous literature on this subject will not be attempted here, and mention will be made only of some of the most important contributions: The earliest mention of extrusion of cartilage from an intervertebral disk due to trauma was made by Virchow1in 1857. Goldthwaite,2in 1911 apparently was the first to direct attention to the possible importance of the condition in producing compression of spinal nerve roots within the spinal canal. In the same year Middleton and Teacher3reported a