Portugal is ageing, and this is a major challenge for the long-term sustainability of its public finances. How to reform its overwhelmingly pay-as-you-go public pension system has dominated the policy debate in the last two decades. But demographic pressures are not the only concern. Far from mature, the full effects of an expanding and often generous coverage are yet to be felt. Also, political manipulation, multiple subsystems, and a very complex set of rules are all troublesome in terms of financial sustainability and economic efficiency. This book has a comprehensive account of how the public pension system evolved. Using a dynamic general equilibrium model with a detailed pension module, parameterized with administrative records, it evaluates all the policy changes enacted until 2007, the last major overhaul of the system. Long-term financial sustainability is assessed, and a reform package is proposed that addresses structural deficiencies and closes the sustainability gap without creating a problem of insufficient pension income. This book is a must-read for anyone in academia or in public policy who is interested in an analytically-sound approach to public pension reform.