Mitral annular velocities derived from tissue Doppler (S', E', A') and left ventricular (LV) end-diastolic pressures were obtained in 11 patients with significant primary mitral regurgitation (MR), 26 patients with significant MR secondary to ischemic or dilated cardiomyopathy, and in 29 asymptomatic controls. The mitral E/E' ratio was related significantly to LV end-diastolic pressure in patients with secondary, but not in patients with primary MR. In patients with secondary MR, a mitral E/E' ratio >15 predicted an elevated LV end-diastolic pressure with a sensitivity of 80% and a specificity of 100%. Thus, the mitral E/E' ratio is a reliable estimate of filling pressures only in subjects with significant secondary, but not with significant, primary MR.