We examine whether restricting a beer distributor's external trading opportunities increases the market shares of brands carried by the distributor. We use distribution status changes from the Anheuser‐Busch‐InBev distribution agreement, along with a panel scanner data set from a grocery chain in California, to implement a ‘difference‐in‐differences’ empirical strategy. We find that InBev's market share increased by 6% once InBev was carried by Anheuser‐Busch's exclusive distributors, while InBev's retail price had no significant change. The effect on InBev's market share is stronger for smaller stores that carry more brands. These results are consistent with the efficiency‐based theory of exclusive dealing.