The serum enzyme paraoxonase (PON1) has a number of disparate activities that can have important consequences for human physiology. It is implicated in drug metabolism and the metabolism of several organophosphate derivatives. Recently, a role of the enzyme in pathogenesis of vascular diseases and in protection against atherosclerosis was proved, based on human and animal studies. The article is a reviewof presently known information about paraoxonase: about structure and polymorphisms of paraoxonase, about its function and mechanisms of action, about connection between oxidative theory of atherosclerosis, HDL and paraoxonase, about localization of paraoxonase in the human body, about relation between cardiovascular diseases, diabetes and paraoxonase, about relation between low paraoxonase activity in serum and other diseases.

        Key words: paraoxonase, polymorphisms, atherosclerosis, cardiovascular diseases, diabetes mellitus.