There is little information on the indications for balloon dilation angioplasty for aortic coarctation. To determine the indications for balloon dilation in aortic coarctation, we evaluated prospectively the outcome of children treated according to our therapeutic protocol. The protocol included patients with postoperative recoarctation and isolated native coarctation with risks for surgical repair as conditions for which balloon intervention was absolutely indicated, and native coarctation without a significant arterial duct as a condition possibly qualifying for balloon dilation. Patients with duct-dependent coarctation and diffuse hypoplasia of the aortic arch were not considered to require balloon intervention and were treated surgically. We entered 47 patients into this protocol between January 1988 and December 1993. In 21, dilation was performed successfully and provided significant relief of pressure gradients. The peak systolic pressure gradients across the coarcted site in native coarctation and postoperative recoarctation decreased significantly from 40±19 to 13±10 mm Hg (p<0.0001) and 38±24 to 14±75 mm Hg (p<0.01) immediately after the procedure, respectively. Similarly, the diameters of the coarcted site increased significantly from 3.8±1.8 to 6.6±2.43 mm (p<0.0001) and 4.6±1.9 to 6.0±2.0 mm (p<0.005), respectively. Five patients with native coarctation, and one with postoperative recoarctation, developed restenosis during the period of follow-up and were treated successfully with repeat dilation. It may be possible to change the therapeutic strategy for aortic coarctation with advances in the use of balloon dilation. Our protocol for this technique appears to be reasonable, but further evaluation of its indications is needed.