Where consumers have imperfect information about specific firms’ prices and lack information about the market, firms have informational market power. In general, improving the consumer’s information about each firm’s price will not necessarily lower average market price. We show, however, that certain types of improvements will lower price. Moreover, a reduction in barriers to entry (e.g., capital costs) will lower price-holding information constant. Where a significant number (but not all) consumers have perfect information, single-price equilibria are impossible.