Anemia is a common condition in critically ill patients.(1) Multiple mechanisms have been implicated in its development, many of which are unrelated to active bleeding.(1-4) Low hemoglobin (Hb) levels are generally related to increased morbidity(1) and mortality,(2) probably as a consequence of the metabolic imbalance between oxygen demands and supply and the sustained hyperadrenergic compensatory response. The gene discussed is GSTM1; the disease is anemia (phenotype).