Two siblings with characteristic clinical and radiologic features of Morquio's disease are presented. Detailed pulmonary function tests, including vital capacity, flow rates, lung volumes, airway resistance, and lung compliance, were performed. The ventilatory studies suggested a restricted pattern due to chest cage dysfunction. Hypoxemia was noted in one patient and was shown to be due to right-to-left shunting, probably related to the microatelectasis as a result of the restricted chest cage.