Hemodynamic studies were performed immediately before, within 1/2 hour and 24 hours after percutaneous mitral valvuloplasty in 31 patients with severe mitral stenosis and pulmonary hypertension. Single rubber-nylon balloon (Inoue balloon) technique was used in all the procedures. Mean transmitral gradient fell from 12.7 +/- 5.4 mmHg to 6.1 +/- 3.1 mmHg (p < 0.001). Mitral valve area increased from 0.9 +/- 0.2 cm2 to 1.8 +/- 0.3 cm2 (p < 0.001). Mean pressure in the left atrium decreased from 21.8 +/- 7.1 mmHg to 16.9 +/- 5.1 mmHg (p < 0.001). After 24 hours there was a significant further drop in left atrial pressure (or pulmonary capillary wedge pressure), that decreased to 11.5 +/- 5 mmHg (p < 0.001). Mean cardiac output increased from 4.1 +/- 0.8 l/min to 4.5 +/- 0.9 l/min immediately after successful valvuloplasty and after 24 hours was significantly higher (5.4 +/- 1.2 l/min; p < 0.001). Mean pulmonary pressure immediately decreased from 29.2 +/- 9.7 mmHg to 26.5 +/- 6 mmHg (p < 0.05) and after 24 hours was 19.4 +/- 6 mmHg (p < 0.001). Left ventricular end-diastolic pressure increased from 9.9 +/- 3.8 mmHg to 13.8 +/- 5 mmHg (p < 0.001). In conclusion, pulmonary hemodynamic and cardiac output improve immediately after percutaneous mitral valvuloplasty and get progressively better up to 24 hours from the procedure.