This study compared the influence of the Trendelenburg position on haemodynamics in non-anaesthetized spontaneously breathing healthy volunteers and anaesthetized, mechanically ventilated patients with ischaemic heart disease scheduled for coronary artery bypass graft (CABG) surgery. Placing the anaesthetized patients scheduled for CABG surgery in the Trendelenburg position resulted in a significant increase in cardiac output and mean arterial pressure and a non-significant decrease in heart rate. In contrast, in the non-anaesthetized healthy volunteers, heart rate increased significantly but both cardiac output and mean arterial pressure changed non-significantly. Further studies will be needed to evaluate the haemodynamics of the Trendelenburg position.