Subluxations of the cervical vertebrae were first described in this country in 1889 by Walton,1 who devised the method of manipulative reduction that bears his name. In 1907 Corner2 reported twenty cases of atlanto-epistropheal subluxations and dislocations, all of traumatic origin, and gave what is probably the best account of the mechanism of their production. The first report of a case of distention subluxation, i. e., subluxation probably due to effusion in the joints concerned, was made by Jacobs3 in 1916. In 1932 Watson Jones4 reviewed fourteen cases from the literature and reported two personal cases. The present paper is based on a consideration of twenty cases of distention subluxation and ten cases of related conditions observed from 1923 to 1933 at the New York Orthopaedic Dispensary and Hospital. ANATOMIC CONSIDERATIONS The atlas and epistropheus articulate through four joints: the atlantodental joint between the anterior atlantal