I examine the choice of sales mechanism by resellers of Major League Baseball tickets.  As the game approaches, sellers tend to switch from using posted prices to using auctions to sell tickets.  This pattern holds within sellers and within seller-ticket combinations, as well as across sellers.  The obvious explanation for this pattern is that auctions increase the probability of sale, which becomes more important as the date of the game approaches, while a posted price gives the seller more control over the price received.  The interesting question is why a posted price is preferred to an auction with an appropriately chosen starting or reserve price which would also limit the seller’s downside price risk while allowing for the possibility of a favorable outcome.  The paper compares explanations arising from the supply side (e.g., auctions are more costly for sellers to manage) with those from the demand side (e.g., buyers prefer buying at fixed posted prices to the uncertainty offered by auctions).