Twenty-five patients presenting with temporomandibular joint dysfunction were examined by both ultrasonography and arthrotomography. Ultrasonography produced an image of the TMJ which was at right angles to the image produced by arthrotomography, since the ultrasound picture was in the coronal plane; with ultrasonography the meniscus became more visible during mouth opening. Anterior displacement of the meniscus was associated with deeper location of the condylar head within the glenoid fossa whilst a perforated meniscus produced a bilobed image. This study has provided a preliminary look at ultrasonography of the TMJ and has shown promise for further work. The present images are not ideal for clinical use but they show the possible potential for non-invasive diagnosis which might be provided by higher resolution ultrasound equipment than that used in this study.