The degree of valvular regurgitation was measured by dynamic magnetic resonance imaging (MRI) and colour-Doppler echocardiography (CDE) in 23 patients (14 men, 9 women; mean age 53 [19-75] years) with aortic (n = 13) or mitral (n = 10) regurgitation. Quantification by MRI was from a section corresponding to the four-chamber view. In aortic regurgitation, maximal regurgitant jet area (JA), ratio of JA to left-ventricular area (JA/LVA) were measured, while in mitral regurgitation, the ratio of JA to left atrial area (JA/LAA) was measured, as well as jet volume (JV) and the ratio of JV to the corresponding volume of the receiving chamber (JV/LVV or JV/LVA). The results were compared with corresponding measurement obtained by CDE in the four-chamber view. The degree of regurgitation was graded as small if JA/LVA or JA/LAA, respectively, was less than 0.2, moderate if 0.2-0.4, and marked if more than 0.4. In the patients with aortic regurgitation the correlation between the two methods was r = 0.91 regarding the jet area, 0.93 regarding JA/LVA and 0.92 regarding JV/LVV and JA/LVA. For mitral regurgitation the r values were 0.93 for JA, 0.89 for JA/LAA, and 0.85 for JV/LAV to JA/LAA. The grading of aortic regurgitation by MRI and CDE agreed in 12 of 13 patients (92%), and in nine of ten (90%) with mitral regurgitation (deviation by one degree of severity in each). These data indicate that quantification of aortic and mitral regurgitation gives similar results with MRI and CDE: thus, MRI is an equal substitute to CDE in patients with inadequate conditions for sonography.