The cases of ninety patients who had tuberculous lesions in the thoracic and thoracolumbar spine were studied. A comparison of the angles of the gibbus deformity at onset and six years later showed statistically significant differences between the patients who underwent treatment by radical surgery and those who underwent treatment by one of two non-surgical regimens. Analysis of the amount of the initial loss of vertebral body and of the final angle of the gibbus deformity at six years showed a correlation coefficient of 0.83. Using the formula y = a + bx, the final angle of the gibbus deformity was predictable with 90 per cent accuracy in the patients who were not treated surgically. The ability to predict the final angle of the gibbus deformity allows the surgeon to select the patients who will require radical resection and bone-grafting to prevent a severe kyphosis.