The right pulmonary artery arising from the proximal ascending aorta is a rare and severe malformation. This retrospective study of 11 children with this condition was undertaken to determine the conditions of diagnosis, to analyse the results of surgery, and, above all, to clarify the mechanism of the left pulmonary arterial hypertension which was always present. Ten of these patients were 4 to 90 days old. All had severe congestive cardiac failure with iso- or suprasystemic left pulmonary arterial hypertension. The only associated lesions were ventricular septal defect (1 case) and patent ductus arteriosus (7 cases). None of the patients had significant left-to-right shunts and only one had left atrial hypertension: this patient died before surgery could be performed. The other 9 patients underwent surgical correction and the pulmonary pressures immediately fell to normal or almost normal values. The child with the ventricular septal defect died of infection 6 weeks after surgery. The 8 survivors are doing well 1 month to 12 years later and left pulmonary pressures are normal in all, including those (5 cases) with a stenosed (4 cases) or completely occluded right pulmonary arterial circulation (1 case) and in 1 patient with obstructive vascular disease. The eleventh patient was very different: she had no signs or symptoms until 2 years of age, when a right pulmonary obstructive arterial disease but with normal left pulmonary pressures was documented. She was not operated on and remains well nine years later.(ABSTRACT TRUNCATED AT 250 WORDS)