Since 1985 balloon angioplasty, followed by surgical repair if angioplasty is unsuccessful, has been used as a treatment strategy for eligible children with discrete native coarctation of the aorta. Although balloon angioplasty has been successful in most patients, this strategy is appropriate only if surgery is safe and effective in children in whom angioplasty does not succeed. To address this issue, the surgical procedure and clinical outcome in 11 children who underwent surgery after unsuccessful balloon angioplasty (defined as a residual systolic gradient greater than 20 mm Hg in 10 and a saccular aneurysm in 1) were evaluated. Data for subjects were compared with data for a control group of seven children who had surgical repair of a discrete coarctation without prior angioplasty during the same time period. In the study group, balloon angioplasty was performed at 4.3 +/- 1.2 years of age, resulting in a balloon/isthmus ratio of 0.98 +/- 0.05 and decreasing mean peak systolic gradient from 54 +/- 3 to 27 +/- 2 mm Hg (p less than 0.001). Follow-up angiography (n = 7) or nuclear magnetic resonance imaging (n = 4) documented a discrete residual stenosis in 10 patients and a small saccular aneurysm in 1. Collateral circulation decreased in three patients. The subsequent surgical procedure and its outcome were similar in the study and control groups. Chylothorax was the only complication, occurring in one child from each group. No paraplegia or mortality occurred. Pathologic examination revealed irregular intimal surfaces with small flaps of intima in 5 of 10 resected specimens from the study group and in 2 of 6 from the control group.(ABSTRACT TRUNCATED AT 250 WORDS)