Background: Since the 1990s, people with intellectual disability (ID) in the Netherlands have been moving from institutions to supported accommodation in the community. The Government is in need of recent data on the numbers of these people, to ensure adequate care provision and funding. This paper reports on the prevalence of people with ID in the Netherlands. The research question was: what is the lowest and highest estimation of prevalence of people with ID in the Netherlands? Methods: Two extrapolation methods were used, each consisting of a number of stages, using general practice databases and ID care services records. Results: The prevalence of people with ID in the Netherlands was 0.7% (111,750 persons). Other assumptions yielded 0.54-0.64%. Arguments for the two extrapolation methods and the lowest and highest estimation of prevalence are discussed. Conclusions: Compared with 1988, there has been a slight decrease in the prevalence of people with ID in the Netherlands, even though we included all age groups and even people with ID of who were not included in ID care services records. By using general practitioner databases it was possible to identify these not registered people with ID.