This article examines the impact of Wal-Mart Supercenters’ entry on incumbents’ pricing behavior and demand. Using a structural model and milk data from the Dallas/Fort Worth supermarket chains, empirical results show that an expansion of Supercenters caused incumbents to price milk significantly more competitively, dropping on average 22.5% between 1996 and 2002, in spite of declines in their milk demand. Furthermore, consumer gains exceeded incumbent losses, lending further support to the notion that Wal-Mart is good for competition and consumers.