Sustainability of Pension Systems in the New EU Member States and Croatia is part of the World Bank Working Paper series. These papers are published to communicate the results of the Bank's ongoing research and to stimulate public discussion. This study finds that pension reforms in recent years have improved the efficiency and sustainability of pension systems in the new member states of the European Union and Croatia. However, for many countries, these probably have not gone far enough to ensure long-term sustainability, given the aging of the population. Reforms have included changes to Pay-As-You-Go (PAYG) systems, including increases in retirement ages (not at least for women), new benefit formulas, and new indexation mechanism. Some countries (Latvia and Poland) have further strengthened the link of contributions and benefits to the sustainability of the PAYG system through the introduction of national defined contribution accounts. The link is strengthened also by moving to a point system, which has been adopted by many of the countries. Several countries have introduced a second, private, pension pillar, funded through diversion of part of the pension contributions, thereby diversifying risk. However, some countries (in particular the Czech Republic, Slovenia, and Romania) will need to do more to safeguard the long-term viability of their pension systems, while others face challenges to ensure equitable pension systems and adequate living standards for all elderly people.