The stability under reaction conditions of realistic Ag/alpha-alumina model catalysts prepared by an appropriate wet chemical route has been studied by AFM and XPS. Although thermal and oxygen-induced sintering of Ag particles on {0001}alpha-alumina are significant, parts per million levels of dichloroethane have a much larger effect. It is suggested that this latter effect is due to AgCl-mediated intra-particle transport of silver. Such chlorine-induced sintering is likely to be the principal cause of the loss of Ag metal area under industrial conditions.