The aim of this study was to confront preoperative echocardiographic data with the anatomic operative findings in patients with mitral insufficiency (MI) undergoing Carpentier's mitral valvuloplasty in order to determine the mechanism(s) of the regurgitation, to classify MI by the echocardiographic changes and to thereby answer the question as to whether echocardiography can identify the patients likely to benefit from this operation. Between February 1985 and November 1987, 66 patients (47 men, 19 women, average age 58 +/- 9 years) with pure MI were referred for surgery with a view to mitral valvuloplasty. This operation was possible in 49 patients (2 of 6 rheumatic MI and 47 of 60 dystrophic MI). The sensitivity of echocardiography was excellent and its specificity very good in diagnosing prolapse of one or the other mitral leaflets. Echocardiography was not as good in distinguishing rupture from elongation of the chordae tendinae and myxoid degeneration from fibro-elastic leaflets. Echocardiography allowed preoperative classification of MI in 4 groups: Group 1 (n = 46) with prolapse of the posterior leaflet; Group 2 (n = 4) with prolapse of the anterior leaflet; Group 3 (n = 8) with prolapse of both mitral leaflets; Group 4 (n = 2) with abnormalities of the mitral annulus alone. Carpentier's valvuloplasty was possible in 43/46 patients in Group 1, 2/4 patients in Group 2, 1/8 patients in Group 3 and 1/2 patients in Group 4. In conclusion, echocardiography is a good tool for selecting patients with dystrophic MI for Carpentier's valvuloplasty.