Asymmetric dimethylarginine (ADMA) is an inhibitor of endogenous nitric oxide synthase (NOS), which inhibits the formation of vasoactive substance, nitric oxide (NO), and further results in endothelial dysfunction. Some studies have shown that ADMA may cause the occurrence and development of memory impairment and dementia through being involved in cerebral blood flow reduction, atherosclerosis, leukoaraiosis and oxidative stress. So, interference of synthesis or metabolism of ADMA may bring forward a new means to prevent and treat cognitive impairment.