The effects of propofol on cardiovascular dynamics were studied, by means of SO2 Swan-Ganz catheter, in 12 patients scheduled for elective pulmonary resection and in 10 patients undergoing closed heart mitral valve commissurotomy. Myocardial contractility was also investigated in 10 patients (5 pulmonary and 5 mitral valve patients) by means of transthoracic echocardiography. The patients were premedicated with morphine (0.1 mg/kg i.m.), scopolamine (0.005 mg/kg i.m.) and diazepam (0.1 mg/kg p.o.). Anaesthesia was induced with propofol (2 mg/kg i.v.) and fentanyl (0.005 mg/kg i.v.) and maintained with propofol (6 mg/kg/h) plus fentanyl (0.005 mg/kg/h) infusion. Muscle relaxation was assured by pancuronium bromide (0.1 mg/kg). Ventilation (O2-N2O 50%) was controlled to maintain ETCO2 between 30 and 40 mmHg. All the patients undergoing pulmonary resection were intubated with double lumen endotracheal tube. Measurements were performed with the patients awake, after induction, during steady state anaesthesia, before and after thoracotomy. Propofol together with fentanyl significantly decreased arterial pressure (more than 35%) and cardiac index (more than 40%) in both groups of patients; heart rate showed no significant changes even after intubation. Right atrial pressure didn't change meanwhile wedge pressure showed a reduction, with statistical significance only in pulmonary patients. Total systemic resistances didn't show any variation in both groups of patients. The echocardiographic data revealed an important impairment of myocardial contractility after bolus of propofol, mainly in cardiac patients, as evidenced by decrease of ejection fraction values (20%) and by increase of left ventricle end systolic volume index (10%) from baseline. SVO2 and DO2/VO2 ratio values were stable, according with deep anaesthesia level and adequate metabolic balance. In pulmonary patients, during one lung ventilation, the intrapulmonary shunt values did not differed either during or without propofol infusion, thus suggesting that propofol doesn't interfere with pulmonary hypoxic vasoconstrictor response. In conclusion an aware use of propofol and a careful haemodynamic monitoring would be advisable primarily in patients with a well known or supposed cardiovascular disease.