We tested the hypothesis that diaspirin cross-linked hemoglobin (DCLHb; Baxter Healthcare Corp.) would improve blood pressure, organ perfusion, and mortality during sepsis. Rats were catheterized to assess general hemodynamics (protocol 1) or regional blood flow (protocol 2). Sepsis was induced by intraperitoneal introduction of a cecal slurry (100 mg/kg). In protocol 1, rats received either 100 or 250 mg/kg DCLHb, or albumin at 1, 2, or 4 h after sepsis induction. Hemodynamics were recorded at these times and daily for 72 h. DCLHb increased blood pressure, prevented 72 h leukocytosis, and reduced mortality, but the timing of DCLHb administration was crucial. In protocol 2 only moribund septic animals received 100 mg/kg DCLHb or iso-oncotic albumin i.v. Hemodynamics and regional organ blood flows were measured at baseline, immediately before and after treatment, and at 24 h. DCLHb immediately increased blood pressure with no changes in cardiac output, heart rate, or regional perfusion. DCLHb increased regional perfusion to vital areas at 24 h (compared to albumin group). Distribution of cardiac output in albumin-treated rats was significantly skewed toward skeletal muscle at a time when cardiac output was significantly lower as compared with DCLHb treated animals. In conclusion, DCLHb safely elicited a pressor response, and improved regional perfusion to selected tissues. However, DCLHb benefits were best obtained when given within a specific time frame.