The economic cost of caring for people with intellectual disability (ID) is extremely high for families, health systems and society. These costs have been significantly underestimated. We show that when all costs of care for a person with ID are considered, that they average US$172,000 per person per year, accumulating to millions of dollars over a lifetime. There are many thousands of genetic conditions that are associated with ID, all with significant impacts on the lives of families. Improved diagnosis of ID through genomic testing provides the opportunity to reduce the costs of uninformative diagnostic tests, allows for informed reproductive decisions, and where possible, for disease specific management. (By Dr Brett Doble, https://jmg.bmj.com/content/early/2020/01/24/jmedgenet-2019-106445 )