We have studied the haemodynamic effects of a bolus injection of propofol 2 mg kg-1 in 20 patients with good ventricular function undergoing aortocoronary bypass surgery. Heart rate and systolic and diastolic systemic (SAP, DAP) and pulmonary arterial pressures, central venous pressure, pulmonary artery wedge pressure, cardiac output (CO), right ventricular ejection fraction, systemic (SVR) and pulmonary vascular resistances and left ventricular stroke work index (LVSWI) were measured before and at 1, 3, 5, 10, 20 and 30 min after the administration of propofol. At 1 min, maximum decreases were detected in SAP (-26%, P < 0.001), DAP (-17%, P < 0.001), SVR (-22%, P < 0.001) and LVSWI (-23%, P < 0.001). The other variables studied showed no significant variations at any time during the study. We conclude that propofol reduces systemic arterial pressure by a decrease in SVR, but not in CO or ventricular filling pressures.