Adolescent idiopathic scoliosis (AIS) presents as an abnormal curvature of spine with vertebral rotation. It may impact the patient for their entire life. Approximately 0.25% of adolescents will require treatment. Brace treatment is the most commonly used non-surgical treatment for AIS. Its goal is stop the progression and maintain the curve at an acceptable level through the high risk growth phase of adolescence. However, its effectiveness is controversial and the actual biomechanical action of the brace is not fully understood. Recently, the Scoliosis Research society (SRS) created a standard criterion for AIS brace studies. However, to evaluate the effectiveness of the brace treatment, the spine flexibility, in brace correction and patient's compliance should also be included in a study. Although bracing has been used for more than 50 years, there are still many unknowns. How much wear time per day is needed for an optimum treatment outcome? How much brace tightness is optimal? What is the best weaning protocol? What is the best method to determine the curve flexibility? How much in-brace correction is needed to obtain good results? Without accurate and precise methods to objectively measure or answer the above questions, it is misleading to state whether or not brace treatment is effective. Therefore, a lot of research is still required before one can answer the effectiveness of the brace treatment.