The cases of 72 patients with spinal tuberculosis who were treated with anterior intervertebral fusion at the Department of Orthopedic Surgery, Yonsei University College of Medicine between Jan. 1980 and Dec. 1988 were reviewed. With available roentgenograms, the kyphotic angles(A) of 15 children below 15 years old and of 57 adults above 16 years old were measured. Results of this study were as follows. 1. The mean increments of the kyphotic angles between postoperation and last follow-up were 12.8 degrees in children who were followed for 1 year and 10 months, and 4.7 degrees in adults who were followed for 1 year and 7 months. The cases with more than 10 degrees increase of kyphotic angle were 66.7% of children and 24.6% of adults. 2. The children had a maximal increase of 5.9 degrees during the first three months after the operation, and the adults had a similar increase during the entire period. 3. The causes of the increased kyphotic angle were 4 cases of graft absorption, 3 cases of nonunion and 3 cases of growth imbalance between anterior and posterior part of the vertebrae in children, and 7 cases of graft absorption, 2 cases of graft fracture, 3 cases of nonunion and 2 cases of recurrence in adults. 4. The mean time of union was 10.8 months in children and 6.5 months in adults. 5. The mean increments of the kyphotic angles, according to location of the involved lesion, were maximum in cervical spine, followed by thoracic, thoracolumbar, and lumbar spine. 6. The mean increments of the kyphotic angles were proportional to the number of involved vertebrae. 7. The mean increments of the kyphotic angles according to the graft bone were maximum in the allograft, followed by the autogenous rib, and the autogenous ilium. The statistic difference was significant between the autogenous grafts and the allograft. Consequently the risk factors for the increase of the kyphotic angle were the growing children, the lesions involving other than lumbar spine, more than three involved vertebrae, and the use of an allograft. The main cause of the increase of the kyphotic angle will be considered to be graft failure before the union. For the prevention of the graft failure, should use an autogenous graft if possible and a prolonged external support and rest untill complete consolidatian. Particularly, the posterior spinal fusion should be planned at least within three months in the children with the combined risk factors.