Introduction Strategic environmental assessment (SEA) is a tool for assessing the environmental implications of actions higher in the planning process than the project level. Whereas in the USA, the National Environmental Policy Act 1969 (NEPA) (1) made no distinc- tion between different decisionmaking levels, European Directive 85/337/EEC (amended by 97/11/EC) included requirements only for the environmental assessment of projects. European requirements for impact assessment above the project level should come into force in 2004, three years after the adoption of the SEA Directive (2001/42/EC) which applies to plans and programmes but not to policies (EC, 2001). To date, there has been considerable political and administrative resistance to the mandatory use of environmental assessment at `strategic'decisionmaking levels (that is, at levels above the project level) in the European Union. This resistance has been based on the argument that SEA application was not beneficial and that the environment was sufficiently considered in existing decisionmaking procedures (see, for example, DETR, 1998; IEEP, 1994). This widespread resistance was the main reason that the European Commission took more than a decade formally to propose the SEA Directive, which was agreed only after much discussion and negotiation. Although SEA requirements should lead to better consideration of environmental aspects at decisionmaking levels above the project level in the European Union, this paper suggests that the full potential of SEA as a decisionmaking tool for supporting sustainable development is unlikely to be reached under the current requirements. There has been relatively little comparative research on an international scale that would provide a sufficient empirical basis for the categorisation of types of SEA. Many of those studies dealing with international practice have relied on second-hand data and often refer to the same well-known set of assessments (see, for example, the critical Policy, plan, and programme environmental assessment in England, the Netherlands, and Germany: practice and prospects Thomas B Fischer Institute for Regional Development and Structural Planning (IRS), Flakenstrasse 28 ^ 31, 15537 Erkner (bei Berlin), Germany; e-mail: thomas.b.fischer@iname.com Christopher Wood, Carys Jones EIA Centre, School of Planning and Landscape, The University of Manchester, Oxford Road, Manchester M13 9PL, England; e-mail: cejones@man.ac.uk Received 21 November 2000; in revised form 27 April 2001 Environment and Planning B: Planning and Design 2002, volume 29, pages 159 ^ 172 Abstract. An analysis of existing (broadly defined) strategic environmental assessments (SEAs) in the spatial/land-use and transport sectors in England, the Netherlands, and Germany concludes that substantial practice exists and that three assessment types can be distinguished, each associated with distinct methodological tasks. By utilising existing terminology, these can be labelled policy- SEA, plan-SEA, and programme-SEA. It appears from current practice that, in order best to meet performance criteria derived from the SEA literature, these three types of SEA should be applied within a tiered system. Although the recently adopted EC SEA Directive includes provisions for the SEA of plans and programmes, the analysis of current assessment practice indicates that consider- ation should be given to extending the formal requirements to cover the SEA of policies as certain tasks are probably better dealt with in policy-SEA than in plan-SEA or programme-SEA. DOI:10.1068/b2787 (1) NEPA was the first legislation worldwide to require environmental assessment.