The ideal solution for volume therapy remains controversial. In cardiac surgery, haemodynamic efficacy as well as the influence of extracorporeal oxygenation are of major interest when administering volume. The present study examines the effects of a new hypertonic saline hydroxyethyl starch solution in comparison to a 6% hydroxyethyl starch solution on haemodynamics and laboratory variables. Patients scheduled for elective aortocoronary bypass grafting received hypertonic saline hydroxyethyl starch (n = 10) or hydroxyethyl starch (n = 10) after induction of anaesthesia in order to double baseline pulmonary capillary wedge pressure. Ten patients without volume therapy served as a control group. Significantly less hypertonic solution than standard solution was effective in doubling pulmonary capillary wedge pressure. Fluid requirements in the patients who received the hypertonic solution were significantly less during, as well as after, cardiopulmonary bypas in comparison to those in the other groups. Cardiac index increased most in the patients who received the hypertonic solution (+34.8%), as did right ventricular end-diastolic volume. Patients in that group showed the highest decrease in total systemic resistance (-29.8%), whereas arterial pressure and right ventricular ejection fraction remained almost unchanged in all groups. No negative alteration in coagulation or organ function was demonstrated within the investigation period. It can be concluded that hypertonic saline hydroxyethyl starch solution seems to be a valuable alternative to conventional volume therapy in cardiac surgery.