Background : Determination of left atrial (LA) size and volume is important in clinical decision-making. The LA anteroposterior dimension (APD) has been routinely reported as LA size assessment with limited accuracy. In measuring the LA volume, Live 3-dimensional (3D) echocardiography has showed good correlation with cardiac MRI. At present, however, it doesn`t become wide-spread. So we compared the several 2-dimensional (2D) echocardiographic measurements with live 3D echocardiography in assessing the LA volume and examined the correlation between them. Subjects : We studied 63 subjects with different LA sizes. Each patient was exmained with both 2D and 3D echocardiography. On the basis of APD of LA with cut-off value of 4.5cm, we classified subjects into LA enlargement (LAE) group and normal sized LA (NSLA) group. LA volume was measured with 2D echocardiography by (1) the cubic equation with APD (Cub); (2) the ellipsoidal formula using APD, long axis, and medio-lateral dimension of LA (Ellp); and (3) biplane modified Simpson rule using the traced areas of LA from apical 4- and 2-chambers at end-systole (Biplane) and with 3D echocardiography. Results : LA volumes measured by Cub, Ellip, Biplane, and live 3D echocardiography were 26.63 짹 8.6, 42.5 짹 19.6, 53.3 짹 14.1, and 47.5 짹 11.9, respectively. We compared three 2D echocardiographic methods of measurement of LA volume with 3D echocardiography. Biplane and Ellip methods showed relatively good correlation with 3D echocardiographic method (r=0.65, p<0.01 and r=0.39, p<0.05, respectively). Of 63 patients, 23 patients belonged to LAE group and 40 patients to NSLA group. In NSLA group, Biplane method only was closely correlated with 3D echocardiographic measurement (r=0.805, p<0.001). But, in LAE group, there was no correlation between three 2D and 3D echocardiographic measurement. Conclusion : In assessment of LA volume, Biplane mothod among several 2D echocardiographic measurements is relatively useful but not accurate in patients with enlarged LA, in whom accurate determination of LA size or volume is important prognostically. This emphasizes the need of more accurate, simple method in measurements of LA volume, for example, live 3D echocardiography.