 It has been recognised that exogenous antioxidants may be useful in sepsis and more recently the potential for antioxidants acting specifically in mitochondria has been highlighted. Antioxidants targeted to mitochondria reduced organ damage in a rat model of sepsis. Although endogenous melatonin is primarily recognised for regulation of the sleep-wake cycle, higher concentrations have potent antioxidant activity with highest levels in mitochondria, and thus stabilise the mitochondrial membrane. Metabolites of melatonin also have antioxidant activity and products from the reactions with oxidant species are also antioxidants. 