On December 23, 2003, Agriculture Secretary Ann M. Veneman announced that the United States Department of Agriculture had diagnosed the first U.S. case of bovine spongiform encephalopathy (BSE), commonly known as “mad cow disease.” This study uses supermarket sales data to analyze the effect of the BSE announcement on U.S. retail beef sales, finding a statistically significant disruption of sales. In addition, we develop a forecast of retail beef sales revenues in the hypothetical absence of BSE. The forecast implies that the BSE announcement may have reduced domestic retail beef revenues in excess of $11 billion in the post-BSE period.