The high local concentration of cholesterol in foam cells has been reported to formulate cholesterol crystals, which trigger a local inflammatory response ( 1 ). Intracellular crystals also induce apoptosis of foam cells, leading to further attraction of macrophages and development of a lipid-rich necrotic core 2 . These effects may suggest a potential contribution of cholesterol crystals to plaque destabilization. Frequency-domain optical coherence tomography (FD-OCT) enables visualization of cholesterol crystals in vivo ( 3 ). We investigated the impact of cholesterol crystals on plaque vulnerability in stable patients with coronary artery disease.