Balloon coarctation angioplasty (BCA) was performed in eight patients (five male and three female) who were 14-49 years old (mean, 27.3 years) with isolated discrete unoperated coarctation of the aorta (n =7) and postoperative recoarctation (n = 1). BCA was successful in seven of eight patients, resulting in a decrease in the gradient (64+19 to 16±13 mm Hg, p <0.01), an increase in the diameter at the coarctation site (0.9± 0.4 to 1.6± 0.4 mm, p <0.01). Follow-up (6 months) has demonstrated continued gradient relief (6±9 mm Hg) and diameter increase (1.6 ±0.2 cm). Monitoring was performed by transesophageal echocardiography (TEE) during BCA, and before and after BCA angiography and after BCA computed tomography. In three of seven patients, immediately distal to the BCA site, intimal flaps (1-2 cm) could be detected by TEE but not by angiography or computed tomography. Follow-up TEE showed spontaneous healing in two and persistence in one patient. By TEE and computed tomography in one of eight patients during follow-up, intima and media dissection was found with pleural effusion and spontaneous healing. In one female patient, aortic dissection occurred after successful uneventful BCA, detected by TEE at the 6-month follow-up study and subsequently confirmed by biplane angiography, not detected by computed tomography and previous monoplane angiography. Because of the significant morbidity of BCA in this group of patients, its role in the management of adults with coarctation has yet to be determined. Further long-term follow-up studies will demonstrate whether the observed intima and media dissection by TEE after BCA are related to aneurysm formation. (Circulation 1990;81:805-814) C oarctation of the aorta is usually detected during childhood, and the patient is referred for surgery. Percutaneous transluminal angioplasty (PIA), introduced by Gruentzig in 1977 for coronary arteries, was rapidly adopted as a method for treating children with pulmonary and aortic valve stenosis.1-4 Even cases of peripheral stenosis of the pulmonary artery have been successfully dilated.5 Because it was demonstrated that it is possible to perform postmortem PTA for coarctation of the thoracic aorta,6 this procedure has been successfully used in children.7-14 Reports of aneurysm formation15From the II.