<正>To clarify the contribution of left atrial pressure to the secretion of beta-endorphin, we have investigated the relation between plasma beta endorphin levels and hemodynamic changes in 35 patients with mitral stenosis undergoing percutaneous transvenous mitral commissurotomy (PTMC). Before PTMC, plasma beta-endorphin levels obtained from the antecubital vein (28.91 ± 5.59 pg / ml) and from the femoral vein (28.20 ± 5.44 pg / ml) in the patients with mitral stenosis were significantly higher than those obtained from the antecubital vein in the healthy volunteers (22.59 ± 3.86 pg / ml, n = 34, P< 0.001 for each). The levels of beta-endorphin in the femoral vein correlated well with the mean left atrial pressure (r=0.777, P< 0.001) and the mean right atrial pressure (r = 0.450, P<0.01) before the procedure. The antecubital venous levels of beta-endorphin in patients in New York Heart Association functional Classess Ⅱ (26.45 ± 5.39 pg / ml, n = 20) and Ⅲ (32.20 ± 4.02 pg / ml, n = 15) were significan