A review of the roentgenograms and clinical findings of 100 patients seen consecutively who had had halo-pelvic distraction for the correction of spinal deformity showed an overall incidence of cases with apophyseal joint degeneration of 47.4%. There were independent and significant differences between the asymptomatic and symptomatic groups with regard to patients' ages and the amounts of the time spent in halo-pelvic distraction. Stepwise discriminant analysis has yielded a table of the maximum amount of time a patient can spend in halo-pelvic traction per year of age, beyond which there is a significant chance of developing degenerative changes.