This issue, "On Counting What Matters: Finding Adults With Intellectual and Developmental Disabilities in Population Health Data," presents an overview of health surveillance research for people with intellectual and developmental disabilities (IDD) in the United States. Although public health now conducts surveillance of people with disabilities broadly defined and compares their health status with that of individuals without disabilities, there are many challenges in conducting health surveillance of people with IDD. Difficulties include how to define cases, how to find cases, and how to obtain accurate information (Krahn, Fox, Campbell, Ramon, & Jesien, 2010). This issue will present critical conceptual and methodological issues, including recent prevalence and population health analyses, along with proposals that can lead to more equitable health and improved health surveillance for people with IDD.