The clinical conditions, roentgenographic findings, and pulmonary function tests of 6 children (mean age, 10.9 years) with surgically treated congenital lobar emphysema (group 1) were compared with those of 5 children (mean age, 10.3 years) with congenital lobar emphysema who had been treated conservatively, i.e., nonsurgically (group 2). At the time of this study, patients in both groups were asymptomatic. Patients in group 1 were surgically treated because of severe respiratory distress in the newborn period, with the exception of one patient, who was eupneic as a newborn and was not operated on until the age of 9 years. Patients in group 2 were eupneic or mildly distressed in the neonatal period and received only conservative treatment. Two patients in group 1 had occasional wheezing and labored breathing, but no patient in group 2 had recurrent respiratory distress. Roentgenographically, at the time of the study, patients in group 1 had generalized overinflation, whereas those in group 2 had only localized overinflation of the involved lobe and minimal compression of remaining lung tissue. Pulmonary function studies in both groups were not significantly different (P greater than 0.05). Both groups had reduced forced vital capacities, large trapped gas volumes, and reduced forced expiratory flows at low lung volumes. Reductions in forced vital capacity were proportional to the unventilated volumes of lung either excised because of congenital lobar emphysema (group 1) or chronically obstructed by congenital lobar emphysema (group 2). These studies suggest that lung growth was not different in these 2 groups and that asymptomatic or midly symptomatic patients do not benefit from surgical treatment.