Abstract: The usage of unleaded gasoline(UL G)was initiated in Shanghai on Oct.1997.In order to explore whether the ULG can decrease the cell membrane toxicity.Two kinds of gasoline including ULG and leaded gasoline(LG)were tested on Engine Dynamometer under the condition of idle and medium-duty.The gasoline exhaust particulates(GEPs)were collected and the or ganic matter adsorbed was extracted.And In vitro Chinese hamster Lung(CHL) cells culture was carries out.Cells were treated with extr acts separately to detect the release of cytosolic enzyme Lactate Dehydrogenase(LDH)and the fuidity of K⁺,Ca²⁺.The results demonstrated that the concentration of LDH in medium and Ca²⁺ insids cells increased and that of K⁺ inside cells decreased accordingly.Doseresponse relatio nships were also found,which suggested GEPs had the ability of damag ing cell membrane and could cause the leakage of LDH,K⁺ out of cell and the inflow of Ca²⁺ into cell.