Diastolic function is an important element of overall left ventricular function. The pattern of flow across the mitral valve is commonly used as a measure of diastolic ventricular function. Magnetic resonance (MR) velocity mapping of blood flow across the mitral valve was compared with Doppler echocardiography. Nineteen patients with known coronary artery disease (mean age, 62 years; 11 with previous myocardial infarction) were studied. The mean value of peak early filling velocity (+/- standard deviation) was 60.1 cm/sec +/- 14.3 with the MR method and 59.4 cm/sec +/- 13.7 with echocardiography (P = .732). The mean difference between the two measurements (95% confidence interval) was -0.8 cm/sec (-5.2 cm/sec, +2.2 cm/sec). The mean value of early deceleration was 4.3 m/sec2 +/- 1.5 with the MR method and 4.0 m/sec2 +/- 1.5 with echocardiography (P = .073). The mean difference was -0.4 cm/sec2 (-0.92 cm/sec2, +0.05 cm/sec2). The mean value of peak atriosystolic velocity was 51 cm/sec +/- 14.6 with the MR method and 62 cm/sec +/- 17.2 with echocardiography (P = .002). The mean difference was -11 cm/sec (-18.1 cm/sec, -3.45 cm/sec). Peak atrial filling was consistently lower with the MR method than with echocardiography. Time-averaged measurements of ventricular filling with MR velocity mapping are an accurate measure of early diastolic filling but underestimate the velocity of atriosystolic filling.