Abstract
Due to its particular institutional context, Belgium has different environmental assessment systems based on separate sets of legislation (federal and regional). All sets contain arrangements on transboundary approaches as well as provisions to assure the quality of the statements or reports. Regarding the intra-Belgian environmental assessment systems, the Espoo Convention has inspired the regional governments to adopt a cooperation agreement. This convention is also applied in the bilateral arrangements of the regional government of Flanders with the neighbouring state of the Netherlands. Internal (at national or subnational level) institutional arrangements have an impact on the feasibility of good impact assessments in a transboundary context. Experiences with transboundary impact assessment may inspire internal policy developments.