The EU is moving towards the full implementation of the Investment Services Directive (ISD). Indeed, in some Member States, implementation has been or will be complemented by further changes to the domestic legal framework in order to cater more effectively for increased competition among financial institutions and markets. This book analyzes these developments from a legal and economic perspective and includes papers written by academics and practitioners from Europe and the US. Some papers examine critical aspects of the ISD from a comparative viewpoint, in particular considering whether further harmonization would be appropriate. Special attention is paid to the regulation of financial exchanges in the new competitive arena and to the need for co-operation between supervisors.