To determine long-term angiographic prognosis after successful angioplasty (< 50% residual stenosis, > or = 20% reduction of stenosis, and no major complications), coronary angiography was performed 2 to 4 years after angioplasty in patients who were < or = 70 years old at the time of treatment and who showed patency (< or = 50% stenosis) 6 months after the initial procedure. Among 407 lesions that were dilated in 333 patients between 1983 and 1989, 298 (73.2%) lesions were reviewed by long-term angiography after 177 +/- 34 weeks. At long-term follow-up, 4 (1.3%) lesions were totally occluded, 3 (1.0%) had severe stenosis (> or = 75% stenosis), 9 (3.0%) had mild stenosis (> 50% to < 75% stenosis), and 282 (94.6%) were patent (< or = 50% stenosis). The percentage of stenosis of patent lesions decreased from 24% +/- 14% at 6 months to 21% +/- 13% at long-term follow-up (p < 0.0001). No specific clinical or angiographic characteristics were identified in patients with severe stenosis at long-term follow-up. These findings indicate that when patency is obtained 6 months after angioplasty, a 95% long-term patency rate with regression of stenosis can be expected.