We have outlined the appropriate study of patients with recurrent respiratory tract infections. A detailed history and a complete physical examination, together with a chest roentgenogram, will, in most instances, give clues to a possible diagnosis. Among the laboratory studies listed in Table 2, the easily available and relatively informative tests consist of routine hemoglobin, white blood cell and differential count, sputum and throat culture for bacteria isolation, screening pulmonary function tests. Most of the other laboratory tests (including sweat tests) and diagnostic procedures require experienced and trained personnel and special facilities and equipment that are available in pediatric pulmonary centers. Any patient suspected of having a complicated or serious pulmonary disease or a congenital anomaly that is correctable by surgery should be referred to a pediatric pulmonary center for a complete diagnostic evaluation. It is important that this be done as soon as possible so that early institution of appropriate therapy may lead to a cure of the pulmonary disorder.