A 65-year-old man, who had undergone the aortic valve replacement with a Carpentier-Edwards pericardial bioprosthesis (CEP 25 mm) 18 years previously (at age 48), was admitted to our hospital with a diagnosis of acute heart failure due to acute aortic regurgitation. Redo surgery was performed. The ascending aorta was cross clamped, and cardiac arrest was induced, and aortotomy was done. One of the leaflets of the CEP was entirely collapsed and dislocated to the LV side, which caused acute aortic regurgitation. Although there was no evidence of endocarditis, the other two leaflets of CEP were severely calcified. Aortic valve replacement was performed with a CEP 23 mm. He was discharged in good condition on the 16th post-operative day.