A 15-year-old boy with recurrent episodes of respiratory failure associated with transient pulmonary infiltrates and a previous episode consistent with pulmonary edema at high altitude was found to have chronic hypercapnia and hypoxemia. The central chemoreceptor ventilatory response to carbon dioxide measured under conditions of hyperoxia was minimal, and there was no ventilatory response to two-breath tests of peripheral chemoreceptor sensitivity. The ventilatory response to mild exercise and the maximal voluntary ventilation were normal. There was evidence of mild maldistribution of ventilation relative to blood flow. The evidence indicated a functional abnormality of the respiratory neurons or the transmission of chemoreceptor information to them. Respiratory failure occurred as a result of deterioration of ventilation-perfusion relationships due to a respiratory tract infection; with the absence of a compensatory increase in ventilation, the ensuing severe hypoxemia and hypercapnia induced pulmonary edema. Similarly, as a result of the absence of a ventilatory response to hypoxemia, the hypoxia at altitude induced pulmonary edema.