Objective: To describe experience with using intraoperative Transesophageal Echocardiography to reliably predict the size of the rapid deployment prosthetic valve by measuring the native aortic annulus Methods: Retrospective review of single institution series of patients undergoing Aortic Valve Replacement with Rapid Deployement Bioprosthetic Valves. Included were patients that had their native aortic valve replaced either isolated or as part of any additional procedure. Aortic annulus was measured prior to initiation of the operation using transesophageal echocardiography (TEE). Correlation analysis was conducted between Echocardiographic annular measurements and actual implanted valve sizes. Results: Twenty five patients underwent rapid deployment valve implantation in the aortic position. Of these, 36% of patients had the same size valve as the measured aortic annulus, 48% of patients had a valve implanted that was 1 mm different, and 16% of patients had 2 mm difference. The mean annular size based was 22.4 mm (range: 21-28 mm). The mean valve size implanted was 23.3 mm (range: 21-27 mm). There was no statistically significant difference between the mean annular measurement and the valve size selected (0.9 mm , p = 0.8). Conclusion: TEE can further enhance valve sizing and guidance through a proper and safe deployment. Although evident in our experience, larger scale studies are needed to further elucidate conclusions on the importance of avoiding under-sizing valves.