International, bilateral and regional agreements have proliferated in the last ten years to twenty years and new ones are still being negotiated. It is thus virtually certain that for some more time to come international investment disciplines will continue to co-exist side by side with different terms and sets of parties, and various degrees of overlap. It is therefore important to understand how these agreements would continue to interact and how their overlaps and differences could be managed in a harmonious way. The present study, with due regard to the complexity of the issues, seeks to increase the level of understanding of the relationships between international investment disciplines, drawing on an analysis of key international investment agreements (IIAs) and OECD's experience with the relationship between its own instruments and other relevant agreements.1 The study is organised as follows. Section 1 broadly states the issues being addressed in the paper ...