The structure of the beef industry has changed dramatically in this century. This phenomenon has given rise to much controversy concerning the competitiveness of the industry in both the economics literature and the courts;One of the key issues in industry organization and antitrust issues is the definition of product and geographic markets. This dissertation attempts three statistical procedures to define markets, each with increasing demands for market information. A fourth procedure is also outlined;Finally, a study of the beef packing industry is conducted within the structure-conduct-performance paradigm, given previously defined product and geographic markets. It was concluded that, although there is presently no evidence of undue monopoly power, the industry may be able to exploit their sizeable market share if they if certain technologies are forthcoming. For example, if beef packers begin to develop branded products for retail, they may be able to influence price at the retail level.