In the Netherlands, a rising number of children are being diagnosed with autism spectrum disorder. It is unlikely that this rise is due to an increase in the prevalence of autism spectrum disorder. There is no indication that the current level of behavioural and emotional problems of children in the Netherlands is higher than 20 years ago. Moreover, the level of behavioural and emotional problems of children in the Netherlands is comparable to that of children elsewhere. This rise might, however, be explained by a lack of reliability in making this diagnosis. Autism spectrum disorders should not be regarded as a disease entity that is either present or absent but as a mix of the behavioural and cognitive characteristics of a child. This change in the concept of diagnosing autism spectrum disorders may enhance diagnostic comparability and result in the needs of children and their parents being better supported.