Fourteen patients with pulmonary vascular disease, either primary pulmonary hypertension or the result of cardiac defects, underwent balloon atrial septostomy (BAS) over the period of July 1981 to June 1988 because of symptoms of syncope, fatigue, right heart failure, and cardiac arrest. Ages ranged from 4 mo to 50 yr. Two moribund patients died within 24 h of the septostomy due to severe hypoxemia and unrelieved low cardiac output; three others died 2 wk to 35 mo later; the remaining 9 patients have improved symptomatically and are alive 11 to 96 mo after septostomy. One received a heart and lung transplant 19 mo later. We conclude that, in patients with symptomatic cor pulmonale secondary to pulmonary vascular disease, atrial septostomy can improve symptoms and may serve as a palliative bridge to heart and/or lung transplantation.