The literature is reviewed that we have not yet seen in the TMJ examination by X-ray, CT and MR associated with the study of lateral pterygoid muscle simultaneously. In this paper we observed the CT and MR images of condylo-pterygo-maxillo-oblique projection (the origin and insertion plane of the lateral pterygoid muscle), In which we can see the relationship between TMJ structures and lateral pterygoid muscle under different functional states clearly. All of the X-ray, CT and MR images were compared with each other for clinical reference.