Aortic valve surgery for the small aortic annulus is still challenging for surgeons. Recently, the new types of high performance prosthesis have been developed and the chance of an aortic root enlargement (ARE) is decreasing. In this study, we propose the ideal strategy of the aortic surgery for the small aortic annulus. We analyzed the clinical records of 158 patients who underwent aortic valve replacement from August 1999 to October 2005 in our institution. The small aortic annulus was observed in 38 patients (24%). Fourteen patients of this group underwent ARE. Patient-prosthesis mismatch (PPM) was less frequently observed in patients with ARE compared to those without ARE. The additional time required for ARE was not considerable, and neither ischemic time nor cardiopulmonary bypass time was significantly prolonged by ARE. In conclusion, we have to select a prosthesis with sufficient orifice area to avoid PPM, otherwise we should choose an option of ARE. For this consideration, we definitely need the chart that demonstrates the relationship between the nominal size of various types of prostheses and the size of a patient's annulus that those prostheses actually fit.