We compared the preoperative and postoperative pulmonary function of thirty-one scoliotic patients ranging in age from nine to twenty-five years. The mean postoperative follow-up period was three years and eight months. Twenty patients were treated by a posterior procedure with Harrington instrumentation. At more than two years postoperatively a significant improvement in the pulmonary function was noted, particularly in patients with a preoperative curve of less than 90 degrees (Cobb angle) and in those in whom the correction was greater than 30 per cent. The remaining eleven patients were treated by an anterior procedure, primarily a Dwyer operation, with or without posterior Harrington instrumentation. These patients manifested no remarkable improvement in pulmonary function more than two years after surgery; three patients showed deterioration. The results of tests performed less than two years postoperatively showed no improvement in pulmonary function, irrespective of the types of assessments used. We attribute our long-term improvements to a shortening of the postoperative period of plaster-cast immobilization and to the use of a plastic corset which allowed relatively free chest motion. We suggest that the Dwyer operation should be restricted to patients with a severe spinal deformity.