In patients with aortic regurgitation (AR), knowledge of the severity of AR, and the degree of left ventricular (LV) dysfunction are important for optimal management. Previous nuclear magnetic resonance (NMR) studies to assess these parameters used multiple tomographic planes that are time-consuming to obtain and analyze, and thus not cost-effective. In addition, these studies assessed the severity of AR by looking simply at the size of the regurgitant jet, a parameter that relates only poorly to regurgitant volume, the present study evaluates a rapid, single-plane, cine NMR approach (scan time <10 minutes), and a new grading system for AR that is based on the presence, size and persistence of not only the regurgitant jet, but also the zone of proximal signal loss. Compared with color Doppler echocardiography (n = 42), the NMR approach detected AR with a specificity of 100% and a sensitivity of 95%. NMR regurgitant jet area correlated well with color Doppler regurgitant jet area (n = 20; r = 0.81; p < 0.01), but did not discriminate well between all grades of AR as compared with x-ray contrast aortography (n = 14). Using the new NMR grading criteria, AR grade by NMR was in accordance with aortographic grade in 12 patients, differing by only 1 grade in the remaining 2 patients. NMR grade was in accordance within 1 grade of Doppler in all patients compared (n = 20). LV volumes and ejection fraction using this single-plane approach correlated well with a previously validated, NMR biplane approach (r > 0.87; n = 18). The NMR approach enables simultaneous assessment of LV function and AR, using practical acquisition and analysis times. © 1993.