This article analyzes the market for experience goods when the product's quality is uncertain. Unlike the case of certain product quality, in this setting, a customer who receives a bad product cannot automatically infer that the producer has cheated. In this two-period model, producers select either high- or low-quality technologies, and consumers individually decide whether or not to rebuy the product in the second period. The sequential equilibria involve mixed strategies in producer honesty and buyer trust, and the form of these strategies under conditions of monopoly and competition is investigated. Unreasonable equilibria are eliminated by applying a form of Kohlberg and Mertens' invariance criterion. Several extensions are analyzed, including the use of first-period discounts and an infinite horizon model obtained by independent repetition of the two-period case. * If product quality is costly and cannot be determined prior to consumption, why should consumers believe a seller's quality claims? Using Telser's (1980) idea of self-enforcing agreements, Klein and Leffler ( 1981 ) developed the now-standard solution to this problem: the price remains above the cost, providing high-quality sellers with rents, and consumers boycott any seller discovered cheating on quality. However, production technologies may have performance uncertainty; that is, the producer might not have perfect control over the quality of each unit. Consequently, the receipt of an inferior product might not always be a clear signal that a supplier is cheating. Given the existence of performance uncertainty, buyers receiving low-quality products do not know whether to blame their problems on malfeasance or on bad luck. This ambiguity can itself increase the seller's propensity to cheat. In this article, we construct and analyze a model of an experience good market with performance uncertainty. The model features fully rational and homogeneous buyers and sellers-there are no arbitrary beliefs or types of player. The setup constrains a buyer's information to his personal experience, rules out any threats to boycott that are not credible