In this chapter we use three case studies (from the USA, Canada, and England) to frame a discussion of key conceptual and methodological issues associated with health-surveillance programs for people with intellectual disabilities. These include the challenges associated with (1) identifying people with intellectual disabilities in administrative databases; (2) identifying people with intellectual disabilities in population-based surveys through data linkage and cognitive testing and self- or informant report; (3) sampling issues; (4) the use of specific intellectual disability surveys; and (5) challenges in measuring health. We conclude with a discussion of the relationship between health surveillance and health policy.