Genetic diseases affect up to 1/50 adults, causing significant complications in many cases. Standard genetic tests often miss the diagnosis, leaving these adults without treatment options and their families without specific risk information. In our study, we used exome and genome sequencing in 47 families who were suspected to have a genetic disease, but remain undiagnosed after extensive genetic testing. We found a diagnosis in 8/47 adults (17%), some of whom had changes to their medical care based on the result. This study highlights the importance of genome sequencing for the diagnosis of adults who would otherwise have been missed by standard of care testing. It will also inform policymakers that this test is cost-effective and could be made a first-line test and should be made accessible to adults with undiagnosed rare disease. (By Salma Shickh, https://jmg.bmj.com/content/early/2020/06/24/jmedgenet-2020-106936)