The domains of the Pediatric Evaluation of Disability Inventory (PEDI) cover self-care, mobility and social function. Employing this inventory as an operational definition of functional performance of everyday life activities, this performance in an age-cohort of children with Down syndrome (DS) was measured at ages 5, 7 (n = 43) and 14 (n = 38). Compared with the performance of typically developing 5-year-olds, this sample was considerably delayed in all three PEDI domains. Improvements were slightly higher from age 5 to age 7, but they continued up to 14 years. Individual differences are evident, however, and also increase considerably with age. A suggested DS functional performance profile receives only partial support. This article argues that observed domain differences should be regarded as a property of the measurement scales, not as a characteristic of the sample. The recognition of substantial individual differences of children with DS is important to rehabilitation.