['The efficacy of coronary stenting of aorto-ostial atherosclerotic lesions is still unclear. We investigated the frequency and mechanism of stent restenosis at this particular lesion.', 'Fifty-five consecutive patients with 64 native aorto-ostial lesions in the right coronary artery (RCA, n = 38) and the left main trunk (LM, n = 26) were treated by conventional stenting. Determinants of angiographic restenosis were established. The mechanism of stent restenosis was evaluated using post-stenting and follow-up intravascular ultrasound (IVUS) findings.', 'Restenosis was more frequent in the RCA than in the LM (50% compared with 19%, P < 0.03) and determinants included diabetes mellitus (63% compared with 21%, P < 0.03), calcium deposition (58% compared with 5%, P < 0.003), smaller stent cross-sectional area (SA) (as demonstrated by post-stenting IVUS studies, 8.1 +/- 1.4 mm compared with 10.2 +/- 2.2 mm, P < 0.01), larger plaque burden (64 +/- 6% compared with 57 +/- 8%, P < 0.03) and less circular expansion at the aorto-coronary junction. Serial IVUS examination was performed in 11 patients with restenosis of the right coronary ostium. The mean reduction in the SA was 21% at the aorto-coronary junction (6.4 +/- 1.9 mm, P < 0.003), whereas the SA at the distal edge was unchanged. Thirty-three per cent of late luminal loss was due to chronic stent recoil.'] Does chronic stent recoil play an important role in restenosis of the right coronary ostium?