Between 1986 and 1990, fourteen patients with univentricular atrioventricular connection and subaortic stenosis underwent surgical treatment. The patients consisted of 7 cases of double inlet left ventricle, 4 with double inlet right ventricle, 3 with tricuspid atresia. The palliative operation was performed in 6 infants ranging in age from 17 days to 6 months. Four patients with mild subaortic stenosis underwent pulmonary artery banding, in two patients this was combined with repair of coarctation of the aorta. Two patients with severe subaortic stenosis underwent the Norwood operation. There were no operative deaths. One of two patients who underwent the Fontan operation 2 years after the Norwood operation died later. The definitive operation was performed in 8 children ranging in age from 4 to 11 years. Five of these 8 patients had previous pulmonary artery banding. Five children with double inlet left ventricle underwent septation combined with enlargement of bulboventricular foramen. Postoperatively all remained in sinus rhythm and had no pressure gradient between Aorta and left ventricle. A Fontan operation combined with a Damus operation was performed in 2 children, 1 of double inlet right ventricle and 1 of tricuspid atresia. In both cases, postoperative angiogram showed no pulmonary incompetence. One patient underwent enlargement of bulboventricular foramen after a Fontan operation. All survived later. Young infants and neonates with severe subaortic stenosis can survive by the Norwood operation. Infants with mild subaortic stenosis, although can survive by pulmonary artery banding, should be closely followed for the development of subaortic stenosis. For relief of subaortic stenosis, enlargement of bulboventricular foramen may be effective in septation.(ABSTRACT TRUNCATED AT 250 WORDS)