Myofascial pain is a condition associated with regional pain and muscle tenderness characterized by the presence of myofascial trigger points. In this case report, a subject complaining of nighttime bruxism was clinically assessed, and a latent trigger point of the anterior temporalis muscle was identified with manual palpation. A surface electromyographic (SEMG) exam of the anterior temporalis muscle harboring the latent trigger point demonstrated several SEMG features, including post-contraction irritability, delayed relaxation following contraction and accelerated muscle fatigue. It was concluded that a SEMG exam may detect abnormal masticatory muscle function and, therefore,assist in the evaluation of myogenous temporomandibular disorders.