In this report the importance of the pulmonary hypertension and the value of the hemodynamic impairment, which is thought to be done with valve replacement at the patients of mitral stenosis, have been observed. Between the period of January of 1991 and July of 1995 the 20 patients, to whom mitral valve replacement have been performed because of fibrocalsific mitral stenosis Cardiovasculary Surgery Department of Medical Faculty of Selçuk University, the hemodynamic parameters are reviewed at the preoperative and early postoperative period. At the patients to whom mitral valv replacement operation have been performed, the decrease in the pulmonary arterial pressure, pulmonary capillary wedge pressure and pulmonary vasculary resistance and the increase at the index of stroke work of right ventricle and stroke volume have been observed. The importance of the evaluation of the ejection fraction of the right ventricle or pulmonary vasculary resistance, which is mostly correlated with this, have been emphasized for the optimum operation time choise at the patients, who should undergo valve replacement.