BACKGROUND Natural history studies have reported that the progression rate of juvenile idiopathic scoliosis (JIS) curves larger than 20° is high and tends to progress. The aim of this study was to investigate the outcome of bracing on JIS and to determine the prognostic factors on the success rate of brace treatment. METHODS From March 1985 to February 2015, the clinical data of all JIS patients with referral age from 4 to 10 years who received brace treatment were reviewed. Those patients with a prebrace Cobb angle >20° and a Risser sign of 0 to 2 were included and followed up a minimum of 2 years after discontinuation of the brace or time of spinal fusion. The Cobb angle was recorded at the time of diagnosis, before initiation of bracing, weaning time, brace discontinuation, and final follow-up. RESULTS From 297 patients with JIS, a total of 75 cases (18 boys, 57 girls) with an average curve magnitude of 31.9° at the time of diagnosis met the inclusion criteria of the study. For successfully treated patients, the average best in-brace correction was 55% for Lenke I curves, 59% for Lenke II curves, 41% for Lenke III curves, and 62% for Lenke V curves. For a total of 27 patients (36%), the brace treatment failed. Of these, 21 patients (78%) reached spinal fusion, and curves of 6 patients (22%) increased to ≥50°. The progression rate was highest in patients with Lenke type III curves (67%), and also in those with a curve magnitude of ≥46° (94%). CONCLUSIONS Brace treatment is an effective strategy for controlling the curve progression and avoiding spinal fusion in JIS. METHODS 4.