Some evidence suggests the increasing prevalence of hypertension in children and adolescents parallels the increase in childhood obesity. However, because the diagnosis of hypertension in children is complicated by variations in the definitions of normal and abnormal blood pressure depending on age, sex, and height, underdiagnosis of hypertension is possible. In an analysis of medical record data from 14 187 children and adolescents seen for well-child care visits over a 7-year period, Hansen and colleagues assessed the frequency of undiagnosed hypertension and prehypertension. The authors report that 26% of the children with hypertension and 11% of the children with prehypertension had the diagnosis documented in their electronic medical record. Patient age, height, and obesity-related diagnoses and the magnitude and frequency of abnormal blood pressure readings were associated with diagnosis and documentation.