Magnetic resonance imaging was compared with echocardiography and angiography in determining the regurgitant volume in patients with aortic regurgitation. Forty patients were examined at 1.5 T. The regurgitant jet was located using a gradient-echo sequence. Cine measurements were performed to calculate left ventricular function. For flow evaluation, a velocity-encoded breath-hold phase-difference magnetic resonance sequence was used. The degree of aortic regurgitation assessed by magnetic resonance imaging agreed with that of angiography in 28 of 40 (70%) patients, and with the echocardiography result in 80%. Correlation between calculated stroke volume by magnetic resonance cine and flow measurements was very good (r > 0.9). Magnetic resonance imaging enables quick and reliable quantitative assessment of aortic regurgitant volume, and it might be the optimal technique for multiple follow-up studies and assessment of left ventricular function, leading to better evaluation of disease severity and optimization of the timing of valve surgery.