Background Preoperative recognition of the presence of bicuspid aortic valve can be important in the planning of procedures. Multiplane transesophageal echocardiography may allow more accurate detection of valvular morphology than does biplane transesophageal echocardiography. Methods and Results The studies of 710 patients who subsequently underwent valvular or aortic surgery were reviewed in a blinded fashion. The inclusion criteria were adequate short-axis view and operative note confirmation of aortic valve morphology. Six hundred eight patients were submitted to further analysis. Four hundred three patients had aortic stenosis as the primary diagnosis. Three hundred sixty patients had biplane examinations and 248 had multiplane examinations. The sensitivity and specificity of the multiplane technique in assessing aortic valve morphology (bicuspid vs tricuspid valve) was 87% and 91%, respectively. The sensitivity and specificity of the biplane technique was 66% and 56%, respectively. Whether valves were calcified or not did not result in major changes in sensitivity and specificity for either technique. Conclusions Multiplane transesophageal echocardiography provides a more accurate assessment of preoperative aortic valve morphology than does the biplane approach in the majority of patients. (Am Heart J 2000;139:1071-6.)