Aim: Peroxiredoxin Ⅱ (prxⅡ), a cytosolic form of the anti-oxidant peroxiredoxin family, has been reported to protect cardiomyocytes from oxidative stress-induced injury.Interestingly, we found that prxⅡ expression levels were decreased to 60％ in failing human hearts, compared to donors.However, the expression levels of this cellular peroxidase were significantly increased in the hyperdynamic hearts of two genetically modified mouse models with: a) phospholamban ablation; and b) over-expression of the active inhibitor-1 of protein phosphatase 1.