\s=b\Thirty children with lower respiratory tract infection of varying degrees secondary to chronic tonsillitis and/or enlarged adenoids were studied clinically and roentgenographically. Symptoms and signs of alveolar hypoventilation and signs of cor pulmonale were present in two of them. These symptoms and signs improved markedly after adenoidectomy and tonsillectomy. The relationship of the lung changes to the incidence of cor pulmonale is discussed. The development of recurrent attacks of severe lower respiratory tract infection secondary to diseased tonsils and adenoids is believed to play an important role in the pathogenesis of cor pulmonale in children with upper respiratory tract obstruction due to chronically enlarged tonsils and adenoids.