Since the 1980s in the Netherlands more and more children with Down syndrome are entering regular schools. Three research questions were explored. 1. What does the development of Down syndrome regular elementary school placement look like expressed in numbers? In chapter 2 and chapter 3, a demographic model for birth and population prevalence of Down syndrome was developed and validated. For the Netherlands, birth prevalence currently is estimated at 14 per 10,000 with around 275 total annual births. The impact of selective abortion is lower than in the UK. Dutch Down syndrome population prevalence is estimated at 7.7 per 10,000 and the total population at 12,600 individuals. In addition, in chapter 4, an estimation was made of the number and percentage in regular schools. The total primary school aged Down syndrome population (specially and regularly placed children taken together) has risen from 1300 in the school year 1985-86 to 2100 in 2005-06. This rise continues until 2010 and then the numbers will stabilize. It can be concluded that the percentage of all children with Down syndrome in the age range 4-13 in regular primary education has risen from 1% or 2% (at the very most about 20 children) in 1986-87, to 10% (about 140 children) in 1991-92, to 25% (about 400) in 1996-97, to 35% (about 650) in 2001-02, and to 37% (about 800) since 2005-06. Nowadays, around 56% of all five year old children with Down syndrome enter a regular school. A little more than 40% of children who have entered a regular school remain in regular education for their entire primary school period. Inclusion in secondary education is still rare. 2. What is the effect of regular versus special school placement of students with Down syndrome on their self help skills, language, academics and social functioning? In chapter 5 (a review of literature) and chapter 6 (a Dutch survey study), it is concluded that regular placement yields better development of language and academic skills, even after the effect of selective placement on ability ...