To determine whether equilibrial dysfunction is the cause or effect of idiopathic scoliosis, patients with idiopathic scoliosis, congenital scoliosis, and comparable controls were tested, using clinical postural tests and electronystagmographic recording of spontaneous and positional nystagmus, smooth visual pursuit, and rotation-induced nystagmus. The scoliosis patients were stratified as progressive or nonprogressive. Dysfunctional responses occurred in the idiopathic progressive and congenital progressive groups, and in two idiopathic non-progressive patients whose curves subsequently deteriorated. These results suggest that equilibrial dysfunction is characteristic of patients with progressive curves, regardless of etiology, implying that it is secondary to the curve rather than a primary event. Seven patients with progressive curves undergoing surgical correction and stabilization were tested preoperatively and 6 months postoperatively. No change in the responses occurred, suggesting the dysfunction persists at least 6 months following arrest of progression.