Radiolucent findings of coronary angiogram are believed to usually represent intracoronary thrombus, but in the present case, were atheromatous plaque with a large lipid core. A 62-year-old man who suffered from an inferior acute myocardial infarction was admitted to hospital 6 h after onset. The first cine angiograms showed TIMI-1 flow in the distal-portion of the right coronary artery, so thrombectomy was initially carried out and TIMI-2 flow achieved. However, the radiolucent lesion did not disappear and so adjunctive mechanical dilatation of the lesion was prformed, which resulted in 'no-reflow' (TIMI-0). Finally, aspiration of the material from the stagnated lesion was attempted and immediately obtained TIMI-3 flow. The retrieved materials were macrophages (foam cells) and many cholesterol crystals, both of which are considered to be atheromatous gruel. Therefore, the sudden flow reduction following percutaneous transluminal coronary angioplasty was caused by mechanical disruption of an atheromatous plaque with a large lipid core.