The index on myocardial contractility of pure mitral regurgitation(MR) after mitral valve replacement is believed to be useful in determining proper operation time before irreversible myocardial damage by volume overload. Thus the authors examined pre and post-operative echocardiographic results of 20 cases of pure MR patients who had been admitted to Pusan National University hospital and compared the usefulness of each index. Pre and post-operative echocardiographic results were as follows respectively ; 1) Left ventricular internal dimension in diastole(LVIDd) were 6.49+/-0.19cm and 5.51+/-0.17cm. 2) Left ventricular internal dimension in systole(LVIDs) were 4.26+/-0.12 and 3.79+/-0.18cm. 3) Ejection fraction were 71.28+/-1.57% and 59.24+/-3.05%. 4) Fractional shortening(FS) were 34.09+/-1.18% and 27.21+/-1.84%. 5) Mean Vcf were 1.53+/-0.08cm/sec and 1.18+/-0.09cm/sec. 6) Left ventricular end-diastolic volume index(EDVI) were 196.35+/-18.33cc/m2 and 98.46+/-9.96cc/m2. 7) Left ventricular end-systolic volume index(ESVI) were 55.28+/-5.12cc/m2 and 41.88+/-6.07cc/m2. 8) Left ventricular end-systolic wall stress/ESVI(ESS/ESVI) were 2.3+/-0.21 and 3.91+/-0.83. ESS/ESVI showed significantly(p<0.05) elevated postoperative change, LVIDd, LVIDs, EF, FS, EDVI, ESVI revealed significantly(p<0.05) reduced postoperative change whereas Mean Vcf had no postoperative change. After examining correlation between preoperative and postoperative results of each index, it is believed that LVIDd, LVIDs, and ESS/ESVI were useful prognostic indices but were unrelated to postoperative ejection phase indices such as EF, FS, and MEan Vcf. Especially in case of LVIDd>6cm, LVIDs>4cm, and ESS/ESVI<2, the prognosis was poor due to myocardial damage by mitral regurgitation.