This report describes the evolution of cathodic protection of reinforced concrete bridges and its current state-of-the-art. It discusses how cathodic protection works, and the effectiveness of the technique. An extensive history of cathodic protection of reinforced concrete is included that covers all aspects of completed projects. There are sections on condition surveys, remedial action, anode systems, design aspects, operation and maintenance, and research and development needs. All of the various types of anode systems are characterized in detail as they have been designed and constructed. The ancillary equipment common to all systems such as power supplies and monitoring equipment are reviewed. Research and development needs are addressed to bring to light the essential research work that is required to further the development and use of cathodic protection of reinforced concrete structures.