Alpha-lipoic acid, a dithiol compound derived from octanoic acid, which acts as a coenzyme for several redox reactions in almost all the tissue of the body. It retains its protective functions in both oxidized and reduced forms. Alpha-lipoic acid reduces oxidative stress by redox generation of other antioxidants such as vitamin C, E and increasing the intracellular glutathione. Exogenous alpha-lipoic acid has been shown to increase ATP production due to its role in the oxidation of pyruvate and alpha-ketoglutarate in the mitochondria. Alpha-lipoic acid administration has been shown to be effective in preventing pathology in various experimental models in which reactive oxygen species have been implicated. Key words: Antioxidant, free radical, alpha-lipoic acid DOI: 10.3329/bjms.v8i3.3982 Bangladesh Journal of Medical Sciences Vol.8(3) 2009 p46-51