This book discusses the theory of bridge bidding for advanced players, with emphasis on the principles that need to underpin an effective bidding system. These include the concepts of Useful Space, Relays, Transfers, Dialogue Bidding, as well as the conflicting needs for a system that is robust, antagonistic, and also accurate. The ideas are illustrated with dozens of example hands from championship play, showing how these principles work in practice. The book will appeal to serious tournament players.