In this article, Professor Dintenfass reexamines entrepreneurial efficiency in the interwar British coal industry. Using previously neglected company documents, he shows that cost-reducing and price-enhancing innovations in coal extraction, organizational practice, and marketing were not widely diffused, though neither geology, finance, nor industrial relations inhibited their adoption. He concludes that mismanagement was an important cause of the British coal industry's misfortunes in the 1920s and 1930s, but that the coalowners' failure to employ the new techniques cannot be attributed to the structure of the industry or to the survival of outmoded forms of business organization.