Strategic Environmental Assessment (SEA) is a new approach to environmental assessment, global in scope, which considers the environmental impacts of policies, plans and programmes. It is already in use in a number of countries and is rapidly being adopted by those involved with environmental management and regulation, including governments, official and voluntary sector agencies, academic courses and consultancies. This text defines and analyzes SEA within the overall context of environmental assessment. It introduces and reviews the current state of SEA, evaluates its application in a number of countries with a range of detailed case studies, provides a critique of its techniques and an analysis of its importance for the future.