Polymerized bovine hemoglobin (PBH) was compared with hydroxyethyl starch (HES) in a hypovolemic shock model. Eighteen dogs were subjected to hemorrhage; systolic arterial blood pressure was maintained at 40 mm Hg for 30 min (mean blood pressure 37.8 ± 4.7 [SD] mm Hg). Resuscitation was conducted by infusing their own shed blood (control group) or 6% HES (mol wt 200,000) in 0.9% NaCl (HES group) or PBH (PBH group), both in an equal amount to the shed blood. Directly after infusion, oxygen delivery and consumption returned to prehemorrhage levels in all three groups. In the HES group, the lowered arterial oxygen content was compensated by a 158% increase in cardiac output, in contrast to an increase of 31% and 9%, respectively, in the control and PBH groups. Early recovery from hypovolemic shock with regard to oxygen transport and delivery in the PBH group seemed to be comparable to the control group, without the increase in cardiac output seen with HES infusion.