Limitation of movement of the back, pelvis, chest wall, and other joints are the consequences of ankylosing spondylitis. The most serious problem is severe kyphosis leading to disturbance of the activities of daily living and failure of the respiratory system. Transpedicular decancellation closing wedge vertebral osteotomy, using the posterior approach followed by segmental spinal instrumentation, is a safe and easy technique for correction of the deformity. The authors report the results of this technique in six patients, five men and one woman, who had undergone the operation. The average age of the patients was 29.8 years (range 21-38). Three patients had thoracolumbar kyphosis averaging 104 degrees (range, 80-120), while the others had lumbar kyphosis averaging 46.7 degrees (range, 35-60). The angles of correction in all cases average 33 degrees. Only one case in this report had dura tear due to adhesion between the dura and the ossified ligamentum flavum, which required exploration and repairing with myofascial graft. No case had any neurologic complication. At an average of 24 months' follow-up, all cases had improvement of their general appearance, posture, respiratory and gastrointestinal functions, and had good bony union.