The aim of this study was to compare 6% hydroxyethyl starch 130/0.4 with 4% succinylated gelatin for priming the cardiopulmonary bypass circuit and as volume replacement in patients undergoing coronary artery bypass, in terms of postoperative bleeding, blood transfusion requirements, renal function, and outcome after surgery. Forty-five patients received 6% hydroxyethyl starch 130/0.4 (Voluven) and another 45 were given 4% succinylated gelatin (Gelofusine) as the priming solution for the cardiopulmonary bypass circuit as well as for volume replacement. Postoperative bleeding was quantified from the hourly chest drainage in the first 4 h and at 24 h postoperatively. The baseline characteristics of both groups were similar. In the hydroxyethyl starch group, the total amount of colloid used was 1.9 +/- 1.0 L, while the gelatin group had 2.0 +/- 0.7 L. There was no significant difference in hourly chest drainage between groups. Blood transfusion requirements, estimated glomerular filtration rate, extubation time, intensive care unit and hospital stay were similar in both groups. It was concluded that 6% hydroxyethyl starch 130/0.4 is a safe alternative colloid for priming the cardiopulmonary bypass circuit and volume replacement in patients undergoing coronary artery bypass surgery.