We performed radionuclide ventriculography before and within 1 week after percutaneous mirtal valvuloplasty(PMV) to evaluate left ventricular(LV) function in 20 patients(3 males and 17 females, mean age of 38±10 years) who were pure mitral stenosis before PMV and less than grade 1 mitral regurgitation developed after PMV. 9 out of 20 patients had atrial fibrillation and 3 patients developed a small left-to-right shunt(Qp/Qs<1.5)after PMV using double-balloon technique resulted in a increase in mitral valve area(0.9±0.3 to 2.1±0.8mm3, p<0.001) and in rest cardiac output(4.2±1.0 to 4.8±1.4 L/min, p<0.005). And also a decrease in mean mitral gradient (16.2±7.0 to 5.2±3.0 mmHg, p<0.001) was noted. Comparisons of LV function by supine bicycle exercise radionuclide ventriculography before and after PMV showed no significant changes in rest LV ejection fraction (LVEF, 55.2±9.7 to 56.1±9.7 to 56.1±11.0%, p>0.05), maximal exercise LVEF(60.9±10.3 to 59.3±11.1%, p>0.05), peak ejection rate(2.02±0.58 to 2.15±0.60 EDV/ses, p>0.05), and peak filling rate (1.04±0.55 to 1.52±0.49 EDV/ses, p>0.05). However, LV and diastolic volume (LVEDV, -29.3±19.0 to +3.3±32.9%, p<0.001), stroke volume (SV, -22.0±22.0 to +11.2±40.0%, p<0.001). and cardiac output (CO, 64.6±54.0 to 100.4±69.7%, p<0.05) with exercise compared to resting values were significantly increased We conclude that PMV resulted in a significant increase in LVEDV, SV, and CO with exercise, but decreased LV systolic performance and no improvement in diastolic filing.