As the long-standing attempt to create an integrated European banking market is showing signs of success, 1 the costs and benefits of the traditional reliance on national banking supervision-and the (de)merits of alternative arrangements-are receiving attention in a lively literature involving both practitioners and academics. While it is too early to draw conclusions, the current episode of financial distress will shed light on some of the issues involved.The fundamental question is straightforward. Should the growing importance of banks that are multinational not only in terms of their asset base but also in their outlook and business models lead to a fundamental restructuring of supervisory arrangements? Or does the current system, combining reliance on national (mainly home) supervisors with minimum standards, mutual recognition and increasing coordination and information exchange across member-states remain preferable for the time being? If not, what are the alternatives, and the criteria on which decisions should be made?A growing theoretical literature explores the implications of alternative regulatory and supervisory arrangements taking account of the interaction between institutional features, informational issues and incentives structures, inter alia. 2 This literature, exploring implications for both financial stability and efficiency, has yielded valuable insights into the tradeoffs involved in choosing between alternative