To assess the incidence and impact on clinical outcomes of subintimal tracking in patients undergoing percutaneous coronary intervention for chronic total occlusion (CTO). Patients at 27 centres were consecutively enrolled when guidewire crossing of the CTO by either the antegrade or the retrograde approach was confirmed by intravascular ultrasound (IVUS). IVUS images were examined to identify the course of the wire. Clinical follow-up at one year and angiographic follow-up at nine months were performed after everolimus-eluting stent implantation. Among a total of 163 patients (59 antegrade and 104 retrograde), subintimal tracking was more frequent with the retrograde approach (24.2% vs. 12.3%, p=0.10). Although there was no difference in the one-year target vessel revascularisation rate between intimal and subintimal tracking with either the antegrade or the retrograde approach, angiographic follow-up revealed greater late loss in the subintimal group compared with the intimal group. Multivariate analysis identified the pre-procedural reference diameter as a predictor of subintimal tracking. Subintimal tracking was more frequent with the retrograde approach. After medium-term follow-up, no negative clinical impact of subintimal tracking was observed in this small study. However, further evaluation of the angiographic impact is needed.