This is the first and leading comprehensive guide to security for costs in international arbitration, including commercial and investment arbitration, providing a text which will be the key resource for those considering, making and ruling on applications for security for costs. It is the first and only work to consider the 40+ factors informing the discretion to award security for costs.The author begins with an introduction and description of the security of costs controversy in international arbitration, and then explains the developing approach of arbitral tribunals to applications for security for costs, with reference to decisions published by ICC and ASA, and statistics of LCIA and decisions of the UK courts when they had the power to grant security for costs in international arbitration. The book features an analysis of the reasons given for restricting security for costs in international commercial arbitration to 'exceptional circumstances' or similar. The author conveys discretionary factors taken into account by the courts and arbitral tribunals in considering applications for security for costs, special considerations for investor-state arbitrations, the correct approach to the exercise of the discretion, the manner of making and resisting applications, appropriate orders to be made on applications, and consequences of orders.This book is written for all arbitration practitioners around the world, including arbitrators ruling on applications. The work would be incidentally useful to litigation practitioners as it necessarily considers applications for security for costs in litigation.