A great deal of advertising appears to convey no direct credible information about product qualities. Nevertheless, such advertising may indirectly signal quality if there exist market mechanisms that produce a positive relationship between product quality and advertising expenditures. Two models of this phenomenon are presented. In each, advertising signals quality in the short run. The models differ in their treatment of the effect of advertising on long-run sales. In the first, all high-quality firms ultimately establish reputations for high quality whether they advertise or not. This is shown to imply that advertising can signal quality if and only if high-quality production requires investments in specialized assets that increase fixed costs but not marginal costs. In the second model, where nonadvertising firms never acquire a reputation for high quality, advertising might signal quality even if marginal production costs are somewhat lower for low quality. These conclusions closely parallel arguments previously made by Phillip Nelson.