Background: This study was undertaken to evaluate the strategy and validity of aortic root enlargement in patients undergoing aortic and mitral valve replacement. Methods: Between January 1999 and December 2008, 78 consecutive patients aged 38.5 ± 9.4 years underwent aortic root enlargement and double valve replacement at our hospital. The body surface area was 1.4 ± 0.18 m2, the aortic annulus diameter was 18.26 ± 1.34 mm, the aortic orifice area was 0.83 ± 0.43 cm2, and the mean aortic transvalvular pressure gradient was 47.5 ± 35.6 mm Hg. The aortic root enlargement was performed using a Dacron patch lined with autologous pericardium on the basis of either the Nuez (n = 36) or Manouguian (n = 42) procedure depending on how narrow the aortic root was. Results: Mechanical prostheses were implanted in all patients. The mean size of the aortic and mitral valves were 20.5 mm and 25.9 mm, respectively. The postoperative mean indexed effective orifice areas of the aortic and mitral valves were 1.13 ± 0.14 cm 2/m2 and 1.56 ± 0.17 cm2/m2 (p < 0.01 compared with those preoperatively), respectively. The postoperative mean aortic and mitral transvalvular pressure gradients were 10.7 ± 2.3 mm Hg and 3.7 ± 1.6 mm Hg (p < 0.01 compared with those preoperatively), respectively. There were no reoperations for bleeding and no heart block. Valve-related complications included thromboembolism, cerebral hemorrhage, perivalvular leakage, and reoperation. There were 2 deaths, 1 early and 1 late, and survival at 1, 5, and 10 years was 98.7%, 97.4%, and 97.4%, respectively. Conclusions: Aortic root enlargement in patients undergoing double valve replacement can be performed safely to avoid postoperative aortic prosthesispatient mismatch. © 2010 The Society of Thoracic Surgeons.