The rare case of a patient with carpal tunnel syndrome caused by thrombosis of a persistent median artery is presented. Progressive pain in the wrist and dysesthesias in the third and fourth fingers were the atypical complaints. High-resolution ultrasonography revealed a bifid median nerve that was compressed by an occluded median artery. The intraoperative findings are described, and emphasis is placed on the importance of using high-resolution ultrasonography for presurgical diagnosis.