How can investors be encouraged to consider more than purely commercial and short-term gains?~~Various sets of investment principles have emerged in recent years. These principles aim to incorporate social, environmental and governance criteria into investment decisions in order to enhance the benefits and reduce the damaging effects of investment for development. Increasing numbers of organisations are signing up to these principles for reasons that range from improving their reputation to minimising risks and improving long-term investment prospects. Yet their impact on sustainable development remains unproven.~~Focusing on four major sets of investment principles – the UN Principles for Responsible Investment (PRI), the Equator Principles, the Environmental and Social Principles of the European Investment Bank (EIB), and the OECD Declaration on International Investment and Multinational Enterprises – Investing for sustainable development? takes a first step in assessing the content, take-up, implementation and impact of investment principles.~~The study finds that the main impact of investment principles on sustainable development so far is mitigation of the worst effects of investments rather than a shift in the underlying basis of decision-making. Investors are generally unwilling to compromise high returns for improved sustainable development outcomes.~~The authors call for better monitoring and measurement of the impact of investment principles, as well as a better understanding of the broader institutional changes required to support~them so the next generation of investment principles can be more ambitious and bring about investment that supports, rather than undermines, sustainable development.