This report gives an objective account of thecurrent state of play of online peer review systems. It provides a comprehensive overview of all the currently available online submission systems, describing their features and offering a framework for analysing and choosing among them. It then presents the results of three specially-commissioned substantial surveys of authors and referees, editors and publishers. The first survey looked in detail at the authors' and referees' experiences and perceptions of using online systems, and explored the impacts on their behaviour. A second survey of editors similarly explored their experiences and perceptions, but also looked at the impact on their journals, including changes in submission volumes and geographical spread, quality, refereeing and administration times, and workflow. The final survey of publishers focussed on their experiences of choosing a system, planning and implementing its introduction, and the subsequent impacts on the journal. The report will be of interest to all those involved in peer review. It will be especially valuable to publishers, societies and journal editors who are contemplating the introduction of an online system, or a possible change to a new system, and to the online system vendors.