The most common of all types of scoliosis is adolescent idiopathic and is seen with equal frequency in boys and girls at low curve magnitudes. Girls, for unknown reasons, have a significantly higher risk for development of curve progression than boys. Pulmonary and cardiac function are not impeded with lumbar curves and significant changes of pulmonary function are not seen in patients with thoracic curves until the curve reaches a level greater than 70° , i.e., a severe curve. This amount of curve and subsequent cardiac and pulmonary changes are often seen later in life in untreated idiopathic infantile and juvenile scoliosis patients and present a threat to life. Patients with adolescent onset idiopathic scoliosis do not usually have such compromise unless severe curves develop. The time of highest risk for curve progression in adolescent idiopathic scoliosis occurs around puberty, i.e., when the growth rate is the fastest.