Temporomandibular Joint Diseases (TMJD) is a term used for disorders involving temporomandibular joint, mastication muscles and structures related with them and for various clinical problems coexisting together. Anamnesis, physical examination, radiology, biochemistry and electromyography (EMG) helps in diagnosing and making the differential diagnosis for all these problems. Among these useful methods, EMG is especially effective in examining muscle and nerve functioning and in the differential diagnosis in such locations.