Between 1993 and 2000, at least 18 countries saw publication of guidelines proposing minimum representation of outside directors on corporate boards. Underlying this movement is an apparent presumption that boards with significant outside directors will make different and, perhaps, better decisions than boards dominated by insiders. As the first-mover in this movement, the United Kingdom provides a laboratory for a "natural experiment" to examine this presumption empirically. We find that UK boards that complied with the exogenously imposed standard were more likely to appoint outside chief executive officers (CEOs). Additionally, announcement period stock returns indicate that investors appear to view appointments of outside CEOs as good news. Apparently, boards with more outside directors make different (and perhaps better) decisions. (C) 2005 Elsevier B.V. All rights reserved.