This thesis explores the complex interplay between international investment law and public health. Besides being closely related to human dignity and the right to life, health is fundamental to poverty reduction, human development and economic growth. In parallel, the development dimension is a conceptual pillar in the health policy discourse as basic levels of social welfare and economic development are of fundamental importance to the achievement of the fullest attainable standard of health. Since foreign direct investment is deemed to promote economic development, it is clear that in abstract terms the linkage between foreign investment and public health may endorse positive outcomes. However, when countries pursue economic growth, their policy makers may have an incentive to lower health standards to promote foreign direct investment. By the same token, foreign investors may be attracted by lower standards in existing regulations to externalize the health related costs which are associated to their business. In addition, countries may not want to adopt higher standards of health protection because of potential investor-state disputes. The mere possibility of such a dispute concerning regulatory measures alleged to have negative effects on foreign property may have a chilling effect on policy makers.The clash between a state’s responsibility to protect public health and its obligations to promote free trade has been broadly discussed by authors.1 What is lacking is an in depth analysis of the relationship between public health and international investment law. In this respect, there are two questions which arise when considering such a connection. What impact have investment treaties on public health in the host states and to what extent may investment treaty obligations collide with states’ obligations to protect public health? Is investor-state arbitration a suitable forum to protect public interests? This thesis aims at providing a fresh approach to these questions. It attempts to systematically review international investment law in the light of public health. While previous contributions have dealt with the interplay between international investment law and human rights law, 3 this thesis offers an in depth analysis of the almost unexplored linkage between international investment law and public health.