Optical coherence tomography is a new intracoronary diagnostic technique that has a higher resolution than other techniques, such as intravascular ultrasound. We used optical coherence tomography to study outcomes after stent implantation in six patients who had undergone percutaneous coronary intervention, and in whom angiography showed normal results after revascularization. Material was observed to protrude through the stent struts in all patients, small dissections were seen at the stent edges in four patients, and there was incomplete stent apposition in four patients. In two patients, small amounts of thrombus were observed to form around the tomography catheter. With optical coherence tomography, it was possible to detect areas in which the results of percutaneous coronary intervention were suboptimal, despite a satisfactory appearance on angiography.