Among OECD countries and beyond a consensus is developing about the importance of public sector transparency. Above all, transparency is an essential ingredient for effective public policy and sustainable growth. In the specific context of international investment, transparency of the rules guiding cross-border transactions, including the provisions laid down in international investment treaties, is of obvious importance for investors. But the issues involved are much broader. The overall level of public sector transparency in host countries – whether linked with the rule of law, procedural fairness, integrity and public involvement in the political process – is recognised as one of the key factors that make investors, foreign and domestic alike, decide where, and whether, to invest. This special focus sheds light on these issues, drawing on the experiences from individual OECD member countries and in the context of international investment instruments...