Our objective is to report on the clinical and radiological outcome following a decancellisation closing wedge osteotomy for the correction of fixed cervico-thoracic kyphosis in patients with ankylosing spondylitis. The only treatment available for severe fixed flexion deformity of the cervical spine in these patients is an extension osteotomy. Traditionally an anterior opening, posterior closing wedge osteotomy is performed with or without internal fixation. We describe a decancellisation closing wedge osteotomy of C7 accompanied by secure segmental internal fixation. Eight patients operated between 1990 and 2003 with mean age of 54 years and minimum follow up of 2 years were retrospectively evaluated. Restoration of normal forward gaze was achieved in all patients. No patient suffered spinal cord injury or permanent nerve root palsy. There was no loss of correction or pseudarthrosis at final follow up. C7 decancellisation closing wedge osteotomy supplemented with secure segmental internal fixation in experienced hands provides a safe and effective treatment for fixed cervico-thoracic kyphosis in patients with ankylosing spondylitis.