This PhD thesis examines the impact of water resources development projects on the transmission of tropical infectious diseases. A particular focus is placed on dengue, lymphatic filariasis and Japanese encephalitis. A hydroelectric dam project in Laos is presented as a case study to demonstrate the health impact for this type of development. The role of health impact assessment is also discussed. The author concludes that water resources development and management projects offer opportunities for infrastructure development and economic growth; yet, if not well-designed, implemented and operated, they negatively affect health and well-being of local and distant communities. There is evidence that vector-borne infections in particular proliferate in areas with poor infrastructure and limited resources. Health impact assessment provides an opportunity to mitigate the negative and enhance the positive effects of water projects. Given the current predictions of water resources development projects, there is a pressing need to institutionalise health impact assessment in the developing world.