The objective of this study was to determine the procedural success rate of balloon angioplasty for branch pulmonary artery stenosis in terms of its clinical impact on the subsequent management of these patients. Most previous studies of balloon angioplasty have concentrated on the initial success rate (50-60%), complications (6-10%), recurrence rate ( approximately 15%), and technical issues. A favorable clinical impact was noted in only 35% of patients. Over a 3-year period (March 1990 to March 1993), 32 patients (17 boys, 15 girls) underwent 34 balloon angioplasty procedures. Their mean age at dilation was 7.6 +/- 4.3 years (range 1.1-19.0 years). Postoperative tetralogy of Fallot and tetralogy of Fallot with pulmonary atresia were the most frequent cardiac lesions (44%). The procedures were "technically" successful in 56% (19 of 34) of balloon dilations on the basis of at least two of the following criteria: an increase of >50% of the predilation diameter; an increase of >20% in the relative flow to the affected lung by radioisotope study; or a decrease in the systolic right ventricular/aortic pressure ratio from 85-100% to <60%. Twelve percent of the patients had transient complications (two deep vein thromboses, one unilateral pulmonary edema, and one pneumothorax). In 17 of 19 (89%) of the patients there was a favorable clinical impact on their subsequent care as based on one of the following criteria: resolution of the stenosis and avoidance of surgical intervention (n = 14); optimization of future surgical procedure (n = 3); reduction in right ventricular pressure to <60% of aortic pressure (n = 13). Five patients who had unsuccessful balloon angioplasty and one with initially successful balloon angioplasty later underwent endovascular stent placement, which also favorably influenced their clinical status. The success rate of balloon angioplasty for branch pulmonary artery stenosis, when measured by strict procedural criteria, is accompanied by a favorable clinical impact in more than 50% of patients. Hence this procedure should be the initial therapeutic modality in this setting despite the relatively high transient complication rate. The use of endovascular stents probably increases the favorable clinical impact.