Consumers are continually making choices among products, the consequences of which they are but dimly aware. Not only do consumers lack full information about the prices of goods, but their information is probably even poorer about the quality variation of products simply because the latter information is more difficult to obtain. One can, for example, readily determine the price of a television set; it is more difficult to determine its performance characteristics under various conditions or its expected need for repairs. This article contends that limitations of consumer information about quality have profound effects upon the market structure of consumer goods. In particular, monopoly power for a consumer good will be greater if consumers know about the quality of only a few brands of that good. This is a significant departure from the literature. Economists have long been interested in the determinants of monopoly power, but studies have always concentrated on the production function or market-size variables. I try to show that consumer behavior is also relevant to the determination of monopoly power in consumer industries. Location theory has also ignored the consumer's lack of information. Since many trips to a store are, in part, quests for information, the location of retail stores can be profoundly affected by consumer efforts to acquire information. I shall also try to show that advertising and inventory policy are affected by consumer ignorance about quality differences among brands. All of these impacts of consumer ignorance have remained unexplored because economists have not developed a systematic analysis of consumer quests for information about quality differences. Information about quality differs from information about price because the former is usually more expensive to buy than the latter. Indeed this is one reason we expect the variance in the utility of quality facing a consumer to be greater than the variance in the utility of price. This difference in the price of information can lead to fundamentally