This practical guide was developed by the WHO Regional Center for Environmental Health Activities (CEHA) in collaboration with the Liverpool School of Tropical Medicine (LSTM) and the WHO Water Sanitation and Health Program. The guide is intended to assist government authorities in: the promotion and protection of human health and the environment early on in the drafting of development policies, the planning of programs and projects to provide directives on the design of terms of reference for consultants in charge of performing Environmental Health Impact Assessment studies, to propose a procedure for the review of assessment reports by national authorities as an instrument of quality control, and to ensure informed decision-making on proposed economic development projects. It is also intended as a framework guide for consultants implementing Environmental Health Impact Assessment studies.