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The requirement to meet more stringent emission standards has focused attention on the effects of gasoline sulfur on automotive emissions. Numerous studies have shown that three-way catalyst performance is severely inhibited by sulfur. A literature review of laboratory studies on the interaction of sulfur with automotive catalyst components provides the basis for understanding impacts on catalyst activity under the variety of conditions encountered in vehicle operation. Under stoichiometric and rich conditions, SO2 formed during combustion is dissociatively adsorbed on platinum group metal surfaces to form strongly bound Sad. Sulfur inhibition results from both physical blockage and electronic effects of Sad, such that low coverage of Sad results in disproportionately higher levels of reaction site blockage. This is responsible for the nonlinear effects observed with increasing fuel sulfur level.