Both AD and paraoxonase (PON) have been reported to be related to lipids and atherosclerosis, suggesting that the PON gene (PON) is a possible genetic risk factor for AD. We found no association of PON polymorphism with severity of atherosclerosis, densities of AD-type, neuropathologic change, or development of AD in 47 AD and 90 nondemented patients. Our study suggests that PON polymorphism does not play a. causal role in the development of atherosclerosis or AD.