Objective: To compare the three-dimensional echocardiographic analysisof left ventricular (LV) synchrony to LV ejection fraction (LVEF) as measuredby two-dimensional (2D) and three-dimensional (3D) echocardiography(ECHO). Methods: This is a prospective study of 71 patients (41 males,aged 49 ± 11 years), 40 of whom with normal cardiac anatomy (ECHO) andelectrocardiography (ECG) (Group N), and 31 with dilated cardiomyopathy(Group DCM). LVEF, volumes and 16-segment dyssynchrony index % (DI)were measured using 3D-ECHO. LVEF (Simpson’s rule) and volumes weremeasured using 2D-ECHO. Data were compared using Pearson correlationcoefficient (r), 95% CI, linear regression equation and Bland-Altman analysis,p < 0.05. Results: DI% ranged from 0.32 to 21.7% (5.94 ± 6.46), 3D LVEFfrom 0.16 to 0.73 (0.51 ± 0.15); and 2D LVEF from 0.2 to 0.7 (0.47 ± 0.17).The correlation coefficient (r) for DI and 3D LVEF was (r): -0.8203, p <0.0001, CI = -0.8844 to -0.7259, linear regression for DI% (x) and 3D LVEF(y) was y = 63.4515 + (-2.0233) x, p < 0.0001. The correlation coefficient(r) for DI% and 2D LVEF was (r): -0.7046, p < 0.0001, CI = -0.7675 to-0.5824, linear regression for DI% (x) and 2D EF (y) was y = 59.345 +(-3.8721) x, p < 0.0001. Conclusions: Good negative correlation betweenLV synchrony (3D-ECHO) and echocardiographic LVEF (2D and 3D) wasobserved in this series.