This reference paper provides health authorities with a guide to the EIA Directive to assist in navigating the EIA process. The EIA Directive is a crucial tool for sustainable development. It applies to a wide range of projects in European Union (EU) Member States, including those co-financed by the EU through its Cohesion, Agricultural and Fisheries Policies. It also applies to projects funded by the financial institutions of the EU, which operate globally and beyond the 27 EU Member States. EIA is ex ante: it refers to the future. It is a forward-looking instrument. EIA provides information about a project to a decision maker before any effects have occurred. This allows for environment and health to be hard-wired into the design of a project. Ensuring a high level of protection of the environment and of human health requires appropriate consideration of the overlapping activities of health protection, health promotion, disease prevention and health services.