The IAEA reports on lessons learned and actions taken after the Fukushima Daiichi Accident. This publication addresses the challenges faced and the ongoing needs of Member State organizations which have been implementing and maintaining post-Fukushima actions. It discusses the actions taken (or to be taken), good practices and describes effective solutions to issues in implementation, verification, qualification and maintenance. Also discussed are the approaches to measuring and maintaining effectiveness of actions as well as an analysis of merits, costs and benefits. Examples in decision making for implementation and follow-up policies, programmes and procedures to ensure sustainability in the long term are presented.