Objective To investigate the etiology and treatment ofsympathetic cervical spondylosis. Methods Eighteen patients who underwent anterior cervical discectomy and fusion for sympathetic cervical spondylosis were reviewed retrospectively. Lateral views in flexion and extension of the pre- and postoperative cervical roentgenograms were analyzed to quantify cervical instability. Results Cervical instability was found at one level in 6 patients, two levels in 9 patients, and three levels in 3 patients. Cervical instability mainly took place at C3-C4 and C4-C5, occasionally at C5-C6 or C6-C7. Cervical epidural block was performed in 14 patients and it was effective in 11 patients. Cervical discectomy and fusion at unstable segement was carried out in all 18 patients. The effective rate was 88.9%. Conclusions Cervical instability in the upper cervical spine was an importmant factor in the etiology of sympathetic cervical spondylosis.Cervical epidural block may provide diagnostic information. Anterior cervical discectomy and fusion are effective to treat sympathetic cervical spondylosis.