Abstract: Several studies find that business groups create value for affiliated companies in developing countries, which are characterized by weak institutions and poorly functioning markets. In these countries, business groups can act as an intermediary between imperfect markets and individual entrepreneurs. This raises the question whether business groups also create value in countries with strong institutions and well-functioning markets, as there are also substantial costs associated with business groups. We investigate the performance of group-affiliated companies in Belgium, and find that these companies significantly underperform compared to stand-alone companies. Moreover, our results suggest that internal capital markets in Belgian business groups result in misallocation of capital.