Background: Current changes in care philosophy and diversity in care arrangements caused the need for a new estimate of the number of people with intellectual disability (ID), based on recent data. Previous estimates were based on client registrations, which was thought unreliable at this time. This manuscript studies the question how many people with ID can be found in (part of) the Netherlands. Methods: Identification of people with ID through a combination of general practice (GP) data bases and service registrations in the province of Limburg. Results: The prevalence of people with ID appeared to be between 0.64% and 0.70%. About 0.21-0.27% were living with family or on their own; 55% of them did not use common ID services. Conclusion: Results are based on a combination of identification methods. Thirteen per cent of uncertain cases led to minimum and maximum estimates of the population. Limitations of the method and alternative ways of data collection are discussed.