Hemodynamic results after valve replacement surgery are well documented, but there are few follow-up studies on pulmonary function. Pulmonary function and hemodynamic studies were made, preoperatively, in 149 patients with predominant, mitral, aortic or combined mitral and aortic stenosis. A sequential postoperative follow-up of the pulmonary function was performed on 88 patients for as long as 125 wk after valve replacement. All patients had reduced preoperative values for forced vital capacity (FVC), single-breath carbon monoxide diffusing capacity (DLCO), forced expiratory volume in one second, peak expiratory flow rate, and maximal flow after exhalation of 75, 50, and 25% of FVC, and increased total airway resistance, resistance during expiration, and residual volume. The aortic group tended toward more normal values. There was significant correlation between the pulmonary function parameters and the hemodynamic data. In the early postoperative period (10 wk), deterioration of pulmonary function was significant in the aortic group and variable in the mitral and the combined groups; these responses correlated with preoperative hemodynamic and pulmonary function status. Between 10 to 125 wk, all patients showed progressive improvement, especially among those in the mitral group. Patients who died during or soon after mitral valve replacement were found to have significantly lower FVC and DLCO and significantly higher peripheral vascular resistance and cardiothoracic ratio. It is concluded that deterioration in pulmonary function is correlated to severity of cardiac dysfunction, and is reversible late after surgery, except in very advanced cases that have poor prognosis.