Eleven patients with coarctation of the aorta (C of A) underwent balloon dilation angioplasty at the University of Arizona from November 1983 to January 1985. Eight had previously undergone surgery and 3 had native C of A. Two operations were considered unsuccessful: 1 in a patient who underwent tube graft--descending aortic anastomosis narrowing and 1 in a patient with a native wedge type of C of A. Overall mean gradient fell from 47 to 13 mm Hg immediately after the procedure. Mean gradient at repeat catheterization in 7 patients (mean 8 months after angioplasty) was 6 mm Hg. Five patients showed a transient increase in the gradient measured on the day after angioplasty, with 3 showing a fairly marked increase. Values returned to levels equal to or less than gradients measured immediately after the procedure. Angiographic findings at follow-up catheterization in 7 patients showed no evidence of aneurysm formation in either the operative group or in the 2 patients with native C of A who had a membrane type of deformity. Mean C of A to ascending aortic diameter ratios increased from 0.44 to 0.80. At repeat angiography, the mean ratio was 0.76 in the 7 patients studied. Further longitudinal studies in these patients are necessary before reaching conclusions about the advantage of this procedure over surgery, but these early longitudinal results are encouraging for the populations studied: postoperative patients and patients with native membrane types of C of A.