This study was performed to demonstrate the ability of intravascular optical coherence tomography (OCT) to identify characteristic vascular responses to percutaneous coronary interventions (PCI). OCT provides cross-sectional images of tissue in situ at approximately 10 microm, rendering detailed structural information. Intravascular ultrasound and OCT images were obtained from 10 patients before and after PCI. Images were evaluated to identify balloon-induced dissections/disruptions, thrombus, cutting balloon-induced vascular changes, tissue protrusion, stent apposition and symmetry, and intimal hyperplasia. The disrupted intima, intraluminal thrombus, depth of balloon-induced dissections, cutting balloon cuts, tissue prolapse, underdeployed struts, and intimal hyperplasia were all noticed with OCT. This is the first report of the use of OCT to identify in vivo human intracoronary pathology after PCI.