A series of 104 arthrotomographic examinations of the temporomandibular joint in 89 patients is described. Those patients with symptoms referable to the temporomandibular joint and not responsive to conservative methods of therapy were selected. The mean patient age was 29 years with a 3:1 female to male ratio. Operative confirmation of arthrotomographic findings was obtained in 40 joints. The arthrotomogram was consistently reliable in predicting the type of internal joint derangement. Anterior meniscus displacement without reduction, anterior meniscus displacement with reduction, and perforation of the posterior attachment of the meniscus were the most significant abnormalities encountered. Jaw locking was definitely associated with meniscus displacement without reduction and meniscus displacement with reduction. The most important pathophysiologic mechanism explaining the arthrotomographic findings seems to be incompetence of the posterior attachment of the meniscus with anterior displacement. Arthrotomography of the temporomandibular joint is a clinically valuable diagnostic test.