The purpose of this study was to describe the imaging characteristics of posterior disc displacement of the temporomandibular joint (TMJ).The study was based on 35 joints with posterior disc displacement and a control material of bilateral TMJ images of 62 healthy volunteers. The images were analyzed, and criteria for posterior disc displacement were developed.Posterior disc displacement was characterized by the disc or a major part of the disc being located posterior to the superior prominence of the condyle. Three subcategories of posterior disc displacement could be identified: a thin flat disc, a grossly posteriorly displaced disc, and a perforated disc with a portion of the disc displaced posteriorly. Posterior disc displacement was not seen in any of the asymptomatic volunteers.Posterior disc displacement of the TMJ is rare but has probably been overlooked in the past because of a lack of well-defined imaging characteristics.