In recent months, the list of large diversified companies that have decided they would be worth more as several smaller, focused companies has grown sharply. In many of these cases, it has been outside pressure from activist investors that has motivated these actions by management—and with some pretty favorable results.But what is driving these strategic actions and what is most important in determining whether breakups create value? To answer this fundamental questions, it is critical to decide whether large, diversified companies have a value recognition problem or a value creation problem. In this article, the authors present and try to integrate the findings of two separate but related research studies on business diversity and size with the aim of identifying their implications for corporate strategy and helping company executives create more value for their investors.The specific reasons for underperformance by large diverse companies vary greatly, but there are a number of potential problems discussed in this article, including organizational “distance,” capital allocation, human capital allocation, cross subsidies, and ineffective governance. Instead of waiting for activist investors to demand a breakup, executives of large diverse companies should be proactive in addressing the potential weaknesses of their organizations. Private equity firms understand how to make diversification work and many of today's executives could learn some valuable lessons from these firms. Large diverse businesses should embrace “Internal Capitalism,” a corporate culture and set of practices that emphasizes the importance of strategic decision‐making that is linked through continuous performance assessment to the corporate goals of boosting efficiency and sustainable growth.