Extralobar pulmonary sequestrations occurring in 15 patients were studied. Twelve of the lesions were discovered during the first day of life; all of these patients died. The lesions occurred more often in male patients (11 cases). Polyhydramnios was present in four infants, and these four plus an additional infant had localized or generalized edema. Associated congenital anomalies were present in ten patients, including three examples each of diaphragmatic hernia and bronchogenic cyst. In one case the extralobar pulmonary sequestration was composed entirely of a congenital cystic adenomatoid malformation. In one other case, congenital adenomatoid malformation was present in a nonsequestered portion of lung. Significant lymphatic dilatation was found in four cases, two of which resembled congenital lymphangiectasis. Hyaline membranes, present in the normal lungs of three preterm infants, were absent in extralobar pulmonary sequestrations.