Perioperative myocardial infarction or ischaemia is a potential consequence of cardiac surgery and elevated free fatty acids can increase the severity of myocardial ischaemic damage. We investigated perioperative changes in serum free fatty acids, and other serum lipids, as a consequence of using propofol infusions for cardiac surgery during cardiopulmonary bypass. Twenty-five patients undergoing elective coronary artery bypass grafting were allocated to two groups. One group of 12 patients was given a continuous infusion of propofol and the other group of nine patients received intermittent boluses of midazolam as a hypnotic agent. Serum lipid concentrations were measured at four periods perioperatively. Changes in free fatty acid concentrations were similar between the two groups. Lipid concentrations related to triglyceride in the propofol group decreased on one occasion but subsequently returned to control value. On the other hand, such values in the midazolam group remained lower than control values. Propofol is not a contraindication as an anaesthetic for cardiac surgery in respect of concern regarding the effects of free fatty acids.