Sepsis is associated with a mortality of nearly 30%. Mortality is due, in part, to an uncontrolled inflammatory response. Matrix metalloproteinase-9 (MMP-9) and heat shock protein 70 (HSP 70) have been suggested to be biomarkers of severe sepsis and may be useful indicators of treatment success. Hydroxocobalamin (HOC), which regulates inducible nitric oxide synthase and increases systemic vascular resistance, may be effective in treating sepsis-induced hypotension and reversing overexpression of inducible nitric oxide synthase. Objective: To compare efficacy of HOC versus norepinephrine (NOR) versus saline in swine with lipopolysaccharide (LPS)-induced endotoxemia.