We sought to determine whether the small indexed effective orifice area (EOAI) increased mortality and morbidity after aortic valve replacement (AVR) in patients over 75 years of age. From May 1999 to July 2005, 77 patients underwent isolated AVR for aortic stenosis. They were divided into 3 groups (S-EOAI : EOAI < or = 0.7 cm2/m2, M-EOAI : 0.7 cm2/m2 <EOAI < or = 0.85 cm2/ m2, L-EOAI : 0.85cm2/m2 <EOAI) for evaluation. We examined the body surface area (BSA), EOAI, and the left ventricular (LV) mass index (LVMI). We found that patients with S-EOAI had less symptomatic improvement (p <0.05, vs L-EOAI) and LV mass regression (p< 0.01, vs L-EOAI). But, their average New York Heart Association (NYHA) class was improved significantly (2.3 +/- 0.8 vs 1.8 +/- 0.7 : preoperative vs postoperative, p=0.001). Furthermore, severe patient-prosthesis mismatch (PPM) had no significant negative impacts on the freedom of valve-related complications (75.1% : S-EOAI group vs 92.0% : L-EOAI group) and the 5-year survival (84.9% : S-EOAI group vs 87.8% : L-EOAI group). In elderly patients, the average NYHA class was 1.9 +/- 0.6 postoperatively (p<0.0001 vs preoperative) and the LVMI showed significant regression (p<0.0001) despite an average EOAI of 0.73 +/- 0.13 cm2/m2. It is important to consider whether the benefits of avoiding PPM overcome the drawbacks of other complicated techniques. In this study, we found that moderate PPM (0.7 cm2/m2 < or = EOAI) is acceptable to elderly patients.