Oxidative stress disturbs organism's homeostasis and leads to excessive reactive oxygen species (ROS) production. Researchers are still focused on antioxidants that help to reduce oxidative stress level and are helpful in treatment of diseases were ROS overproduction is observed. Among those antioxidants is lipoic acid (LA). When applied systemically LA accumulates in tissues and is converted to dihyrolipoic acid (DHLA) by lipoamide dehydrogenase. Both LA and DHLA are biologically active. LA scavenges hydroxyl radical, subchloric acid and singlet oxygen. Moreover, LA is able to chelate transient ions. Therefore, LA is used in diabetic nephropaties, fungi or heavy metal intoxication, liver diseases, neurodegenerative and cardiovascular diseases. This review surveys the antioxidant ability of LA and its role in pathological states where increased concentration of ROS is observed.