One of common injury sites in golfers is the wrist, but ulnar neuropathies at wrist in golfers have been rarely reported. We report a case of ulnar neuropathy within the Guyon's tunnel occurred in a single golfer diagnosed with electrodiagnosis and ultrasound. A 59-year old man suffered from difficulty with extension of left 4th and 5th finger joints and weakness of hand grasping, which had occurred 2 weeks ago and aggravated slowly. He had no sensory disturbance. During recent two months, he had practiced golf for three to four hours daily. Electrodiagnostic study showed that the deep branch of left ulnar nerve was compromised at the wrist (type IIA). Ultrasound study revealed a ganglion cyst within the Guyon's tunnel. Therefore we diagnosed the patient as having ulnar neuropathy (only deep branch involvement) associated with a ganglion cyst within the Guyon's tunnel. (J Korean Acad Rehab Med 2009; 33: 486-488)
