['To compare the efficacy of volume expansion with 3.5% gelatin and 6% hydroxyethyl starch 200/0.5 in patients undergoing cardiac surgery. The second objective was to compare the two colloids in terms of blood losses and allogeneic blood transfusion exposure rate.', 'In this open-label controlled study, patients were randomly allocated to receive either 3.5% urea-linked gelatin (GEL group: n = 55) or 6% hydroxyethyl starch 200/0.5/5.1 (HES group: n = 55) for per- (including priming of the bypass machine) and postoperative volume management with a maximum dosage of 30 +/- 3 mL.kg(-1).day(-1). Volume replacement was guided according to routine per- and postoperative care based on cardiac index, mixed venous oxygen saturation, and diuresis. If additional colloid was required, 4.5% albumin had to be given. The study period comprised per- and postoperative investigations up to 18 hr after surgery.', 'All hemodynamic variables were comparable in both groups. Total study drug was 25.8 +/- 4.8 mL.kg(-1) in the GEL group and 24.5 +/- 6.0 mL.kg(-1) in the HES group. There was no difference in the number of patients receiving albumin solution or in the amount of albumin administered. Total blood loss was higher in the HES than in the GEL group (11.0 +/- 7.8 mL.kg(-1) vs 8.7 +/- 4.0 mL.kg(-1); P < 0.05) resulting in a higher need for allogeneic blood transfusion (HES: nine patients received 12 units, GEL two patients received 3 units; P = 0.026).'] Is 3.5 % urea-linked gelatin as effective as 6 % HES 200/0.5 for volume management in cardiac surgery patients?