Objective To assess the post-brace curve progression and to identify what radiographic or clinical factors may be predictive of deterioration after brace treatment. Methods The medical records of 112 patients with AIS who completed brace treatment 2 years ago and at least 18 years old at final follow-up were reviewed. Cobb angles were measured from radiographs at initial visit, brace prescription, brace weaning(in brace), first out-brace visit and final follow-up. The curve type, location and chronologic age, Risser sign and menarcheal status at weaning were recorded. Outcome was based on changes in Cobb angle between the first out-brace radiograph versus that of final follow-up. Curve behavior was also identified as improvement, maintenance or mild deterioration, and marked deterioration. The percentage of each type of behavior was calculated and analyzed. Results The mean follow-up periods were 8.1 years after diagnosis and 3.8 years after brace treatment. 4.8% secondary curves deteriorated ≥5? and the rate was significantly lower compared with the rate of 16.3% for primary curves(P