The purpose of this study was to determine the diagnostic value of flow convergence region method (FCR) to complement well-accepted techniques in assessing mitral valve area (MVA). Fifty-three patients (39 women, 14 men) were enrolled in the study. Transesophageal echocardiography (TEE) was performed after transthoracic echocardiographic (TTE) evaluation, and all measurements were performed for each patient. Mean MVA values determined by different methods both in TEE and TTE studies did not differ (p = not significant). In 51 (96%) patients, TEE and TTE were feasible and measurements of MVA with FCR correlated well with the conventional methods (r = 0.87, standard error of the estimate = 0.13 cm²). In TEE, MVA determined by FCR also correlated well with that obtained by the “pressure half time” method (r = 0.90, standard error of the estimate = 0.11 cm²). Results of our study confirmed the feasibility and accuracy of FCR. Because TEE provides reliable estimation of MVA by FCR, intraoperative monitoring by TEE should be considered as a comparative alternative method. (Am Heart J 1998;135:207-14.)