Lung function was studied in 24 patients with advanced mitral stenosis scheduled for mitral valve replacement (MVR), and revealed an obstructive ventilatory pattern. Forty per cent of the patients had a forced expiratory volume in 1 s (FEV1)<60% of that predicted in the preoperative period. Twenty-five per cent of those operated upon showed a similar pattern up to 110 weeks postoperatively. A blind study of the effect of placebo and beta2 agonist (salbutamol) inhalation was performed preoperatively and 6 months postoperatively, to evaluate the reversibility of airflow obstruction in these patients, flow volume curve and body plethysmographic measurement of airway resistance (Rex) and intrathoracic gas volume (VTG). Patients in the pre and postoperative period showed a significant difference between the placebo and the beta2 agonist responses for FEV1, FEV1 as percentage of FVC (FEV1% FVC), peak expiratory flow rate (PEFR), flow rate of 50% of expiratory vital capacity (Vmax50), Rex and VTG (P<0.001). We conclude that salbutamol inhalation improves obstructive impairment in patients with MVR pre- and postoperatively.