Transluminal balloon angioplasty (BA) was performed in 27 consecutive patients with coarctation of the aorta (COA), including 7 infants with preductal COA, 7 patients with restenosed COA after surgical repair, and 13 older children and 1 adult with unoperated COA. The patients were 4 days to 27 years old. The balloon was positioned across the COA and inflated sequentially to pressures of 100 and 120 psi, each inflation lasting for 5 to 10 seconds. Peak systolic pressure gradient (PSG) across the COA was recorded and an aortogram was performed before and immediately after BA. PSG also was recorded during follow-up studies performed in 13 patients 3 to 24 months after BA. BA was performed without complications in each patient. Immediately after BA, the mean PSG was reduced from 49 +/- 21 to 10 +/- 7 mm Hg (p less than 0.01), and the mean COA diameter increased from 3.9 +/- 1.4 to 9.6 +/- 3.6 mm (p less than 0.01). After a follow-up period of 3 to 24 months, the mean PSG remained low (15 +/- 11 mm Hg) and the mean COA diameter increased to 10.5 +/- 4.6 mm. BA can be performed safely. It can be a useful palliative treatment in seriously ill infants with COA.