The aim of this study was to determine the reliability of preoperative transthoracic and transesophageal echocardiography compared with the surgical findings in pure or dominant severe mitral regurgitation with respect to: the evaluation of the lesions, mechanism and etiology; the provision of the type of surgery (valve replacement or reconstruction); One hundred and fifty patients were divided into two groups: Group I (N = 120) in which preoperative assessment included transthoracic echo-Doppler coupled with color Doppler in the last 32 patients; Group II (N = 30) operated recently who underwent both transesophageal and transthoracic echo-Doppler examination. In Group I, the sensitivity of transthoracic echo in the evaluation of the etiological was 86% overall [100% in rheumatic valve disease (N = 28), 86% in degenerative or dystrophic valves (N = 72), 44% in endocarditis (N = 9), 87% in ischaemic dysfunction (N = 8)]. The echo evaluation of the mechanism of the regurgitation was also reliable with the exception of ruptured chordae in which direct visualisation of the rupture was only possible in 19 of the 64 cases (30%). The type of surgery predicted by echo was practiced in 87% of cases.