We have demonstrated that self association takes place in culture conditions when we incubate modified ldl with arterial cells. There is direct correlation between associate size and degree of ldl atherogenicity. Lager associates form lipoproteins more cholesterol was accumulated by cultured cells. To prevent associate formation we developed a filtration system. Culture medium was removed from primary culture incubated with modified ldl. In non-stop regimen culture medium was passed over prefilter to catch culture debris and floating cells. Then medium was passed over filter with different pore sizes and finaly it returned to culture.