This paper provides an overview of the way biodiversity issues are dealt with in strategic environmental assessment (SEA) for spatial plans in the Netherlands. Spatial plans are selected as subject of study because 50 percent of all SEA studies executed in the Netherlands are carried out for spatial plans. Secondly, these plans provide an overarching framework for multiple interventions with potential impacts on biodiversity. It is, therefore, important to pay particular attention to biodiversity at the strategic level of a spatial plan. The evaluation is based on five spatial plans that have been subject to SEA, two national plans, two provincial plans and one local plan. Based on these assessments a number of conclusions are presented on the assessment of biodiversity in SEA for spatial plans in the Netherlands. The evaluation of case studies on which this paper is based was undertaken to produce a submission to the Convention on Biological Diversity for the drafting of international guidelines on biodiversity in SEA.