Three cases of reflex sympathetic dystrophy (causalgia) were associated with cervical spondylosis. Two of them were related to sudden cervical trauma. Patients showed burning pain, hyperalgesia in a segmental distribution, and edema of the arms, hands, and fingers bilaterally. Oral administration of guanethidine sulfate was effective in all cases. Our results support the hypothesis that hypersensitivity to norepinephrine plays a role in reflex sympathetic dystrophy.