While the frequency and seriousness of primary varicella pneumonia have been emphasized recently (1-7), information concerning the physiological alterations of this disease is lacking. Dyspnea, cyanosis, and tachypnea are often present and contrast with the few findings on physical examination of the chest. The diffuse nodular pulmonary densities and prominent bronchovascular markings seen on X rays are similar to the changes of sarcoid, miliary tuberculosis, and carcinomatosis (6, 8, 9). Cyanosis, diffuse nodular pulmonary infiltration, and hyperventilation, in combination, point to impairment in alveolar-capillary gas exchange. Since there is no precise definition of the functional abnormalities of primary varicella pneumonia...