Objective: To study the effects of occlusal trauma on the ultra structure of synovial membrane and articular cartilage in rabbits temporomandibular joints (TMJ). Methods: TMJs from six rabbits with occlusal trauma and three control rabbits were studied by transmission electron microscopy. Results: Degenerative changes in synovial membrane and articular cartilage of TMJ were induced following occlusal trauma. The structure of the articular surface was damaged, and chondrocytes in cartilage showed signs of degeneration. The synovial lining cells contained dense accumulations of vimentin intermediate filaments (IFs), which were especially prevalent in the cellular processes as well as paranuclearly. Microvilli on the synovial cell membrane were commonly seen. The “vermiform bodies” in the deeper interstitium of the synovial tissue were also found. Our findings of the punctate adherens between synovial lining cells were described in detail. Conclusions: The occlusal trauma is really a factor inducing degenerative changes of the TMJ. Objective: To study the effects of occlusal trauma on the ultra structure of synovial membrane and articular cartilage in rabbit’s temporomandibular joints (TMJ). Methods: TMJs from six rabbits with occlusal trauma and three control rabbits were studied by transmission electron microscopy. : Degenerative changes in synovial membrane and articular cartilage of TMJ were induced following occlusal trauma. The structure of the articular surface was damaged, and chondrocytes in cartilage showed signs of degeneration. The synovial lining cells contained dense accumulations of vimentin intermediate filaments (IFs), which were especially prevalent in the cellular processes as well as paranuclearly. The “vermiform bodies” in the deeper interstitium of the synovial tissue were also found. Our findings of the punctate adherens between synovial lining cells were described in detail. Conclusions: The occlusal trau ma is really a factor inducing degenerative changes of the TMJ.