This publication is a collection of selected papers from the 3rd International Symposium on Work Ability-Promotion of Work Ability Towards a Productive Aging. It addresses the Work Ability Index (WAI) as an index for evaluating work ability, developed by the Finnish Institute of Occupational Health as a tool for evaluating work ability of workers. The ICOH SC for Aging and Work has promoted the use of this index through international conferences, publications and other means and by constructing an international database based on this index. As a result, today the WAI is used in 25 languages. WAI is becoming an international and multi-cultural technique. This book is a collection of papers that discuss, from a variety of angles, the goal of developing a truly international standard tool that can be used in common internationally, taking into account differences in circumstances among countries, striving towards a common guideline that exceeds national and regional boundaries and can be used for the diagnostic evaluation of work ability and employability.