Together with aging of the Japanese population, aortic valve replacement (AVR) for aortic stenosis (AS) is now becoming more and more common in the elderly. When the aortic annulus is too small to allow an adequate sized prosthetic valve, aortic root enlargement is required to avoid prosthesis-patient mismatch (PPM). However, age-related comorbidities including aortic root calcification bring significant risk in performing aortic root enlargement. In the present study, 40 patients aged 75 years or more who underwent AVR for AS were reviewed to determine whether moderate PPM has a negative impact on the long-term results. Operative mortality occurred in 2 patients (5%) and moderate PPM occurred in 8 patients. There was no significant difference in survival between cases with and without PPM (P = 0.87). Both aortic pressure gradient (PG) and left ventricular mass index (LVMI) measured by echocardiography were signifi cantly decreased in patients with and without PPM. Reduction of PG was significantly greater in patients with PPM than without PPM (P = 0.02). Reduction of LVMI was not different between the groups (P = 0.58). Moderate PPM did not negatively influence survival or reduction of PG or LVMI in patients aged 75 years or older who underwent AVR for AS.