PURPOSE: This study was undertaken to analyze and compare the effects of percutaneous balloon angioplasty(BAP) on postoperative re-coarctation and native coarctation of the aorta(CoA) and to thereby contribute to the development of treatment methods for CoA. METHODS: The subjects in this study were 21 children who had undergone BAP from Jan. 1996 to Dec. 2000 in the Division of Yonsei Pediatric Cardiology. The relation between factors such as pressure and diameter changes across the coarctation segment together with hemodynamic and morphologic variables of children with postoperative re-coarctation and native CoA was analyzed through retrospective study of medical records. RESULTS: Among the 21 cases, 11 children showed a decreased pressure gradient across the coarctation segment of less than 20 mmHg(average : 11+/-5 mmHg) after BAP was performed. In postoperative re-coarctation, the pressure gradient across the coarctation segment significantly fell from 56+/-21(30-90) mmHg to 20+/-13(0-50) mmHg(P<0.001) after BAP, while in native CoA, the pressure gradient decreased from 57+/-13(40-70) mmHg to 22+/-14(10-40) mmHg(P<0.001) after BAP. The diameter of the narrowest coarctation segment was significantly increased in native CoA and postoperative re-coarctation after BAP. The factor that most affected our results was the ratio of isthmic/descending aortic dimension showing an inverse relationship between the ratio of isthmic/descending aortic dimension and pressure gradient after BAP(gamma=-0.473, P=0.030). Complications included one case of femoral artery stenosis, one case of femoral artery interruption, and one case in which seizure occurred two days after BAP due to cerebral thrombosis. CONCLUSION: We conclude that BAP is an effective treatment modality in postoperative re- coarctation and native CoA.