Institutional investors in OECD countries held over USD 65 trillion in assets at the end of 2009, and they are growing fast in emerging economies where Sovereign Wealth Funds still predominate as source of long-term capital. Concerns about short-termism and corporate governance have led to calls for more “responsible” and longer-term investment, especially by institutional investors that manage retirement savings. Long-term investors could provide benefits by acting counter-cyclically, engaging as active shareholders, considering environmental and other longer-term risks and by financing long-term, productive activities that support sustainable growth. This requires transformational change in investor behavior, i.e. a new “investment culture”, and various major policy initiatives. This article has been designed to stimulate discussion on the benefits of long-term investing for growth, sustainable development and financial stability, and regulatory and other barriers that impede such investment. Drawing on existing OECD work and guidelines, it also puts forward tentative policy proposals to encourage long-term investing, thus preparing the ground for further analysis and data collection to be undertaken by the OECD in this area.