The key findings of this preliminary study are that; (1) the majority of sepsis patients are moderately anaemic at admission to ICU, (2) plasma concentrations of HO-1, the inducible isoform of haem oxygenase, are markedly raised in sepsis, (3) IL-10 concentrations, rather than haemolysis, correlate most closely with HO-1, and (4) high HO-1 and IL-10 concentrations, but not anaemia, at admission correlate with disease severity (APACHE II score) and mortality. The gene discussed is HMOX1; the disease is anemia (phenotype).