Ten cases of congenital absence of a main branch of the pulmonary artery have been reported in the literature.1 The diagnosis was made at postmortem examination in seven instances2 and during surgical exploration in two.3 In only one recently reported case1a was the diagnosis made prior to surgery or death. In the two cases we are reporting, diagnosis was suspected on clinical and routine radiographic examinations and conclusively established by angiocardiography. Angiocardiography, pulmonary function studies, and cardiac catheterization were performed by methods previously described.4 REPORT OF CASES Case 1.— A 48-year-old practical nurse was first seen in the outpatient department five years ago. At that time, her chief complaint was of soreness in the chest and frequent sighing. A chest film taken a year earlier at another hospital was reported to have shown a mediastinal tumor. Bronchoscopy was not revealing, and no treatment was recommended.