Options for surgical repair in hearts with univentricular atrioventricular connection and subaortic stenosis. Thirteen patients have undergone surgical treatment because of subaortic obstruction in hearts with a univentricular atrioventricular connection. Nine patients underwent surgical enlargement of the ventricular septal defect and four patients had construction of an aortopulmonary anastomosis and closure of the pulmonary trunk (the Damus-Kaye-Stansel procedure). Two patients undergoing enlargement of the septal defect and two having the Damus-Kaye-Stansel procedure also had a modified Fontan procedure. One patient had complete atrioventricular dissociation after direct enlargement of the ventricular septal defect, which necessitated insertion of an epicardial pacemaker. One patient died within 30 days of the operation after enlargement of the defect and two patients after the Damus-Kaye-Stansel procedure. There was one late death, occurring in a patient who underwent enlargement of the ventricular septal defect. Ten patients have subsequently undergone conventional cardiac catheterization and angiography or transcutaneous Doppler flow studies to assess the relief of the subaortic obstruction. The result has been satisfactory in all. Because of this experience, we now recommend direct surgical enlargement of the restrictive ventricular septal defect for direct relief of subaortic stenosis occurring with a univentricular atrioventricular connection to a dominant left ventricle, inasmuch as it appears to be hemodynamically effective with a low operative mortality and morbidity. The Damus-Kaye-Stansel procedure can also have a role in relieving subaortic stenosis when the atria are connected to a dominant right ventricle. 