Searching for a muscle stretch reflex that is innervated by the high cervical cord, the authors discovered the scapulohumeral reflex (Shimizu)-SHR (Shimizu). The testing maneuver, localization of the reflex center, its clinical significance, and the designation of the SHR (Shimizu) are dealt with in this report. The SHR is elicited by tapping the tip of the spine of the scapula and acromion in a caudal direction. The SHR is classified as hyperactive only when an elevation of the scapula or an abduction of the humerus have been clearly defined after tapping at these points. Two hundred twenty-five patients with cervical spine disorders, 90 normal individuals, and 17 patients with cerebrovascular strokes were examined. The incidence of hyperactive SHR was highest among several neurologic abnormalities in spastic cases with craniovertebral or high cervical lesions, and all cases with hyperactive SHR in the cervical spine disorder group exhibited neural compressive factors at the high cervical region. The major muscles participating in the SHR are considered to be the upper portion of the trapezius, the levator scapulae, and the deltoid. According to the anatomic level of compressive factors and the postoperative course of the activity in hyperactive SHR cases, the reflex center of the SHR is clinically presumed to be located between the posterior arch of C1 and the caudal edge of the C3 body. Hyperactive SHR provides useful information about dysfunctions of the upper motor neurons cranial to the C3 vertebral body level.