Care and research in childhood cerebral palsy (CP) continue to evolve. As our understanding of CP grows more nuanced, so grows our need to describe function, activities, challenges, adaptations of children with CP. In CP, robust means of measuring outcomes are vital to understanding utility of treatments. Research must accurately measure meaningful constructs of children with CP as a reliable ruler to establish if interventions produce useful effects. This article addresses the challenges of outcome measurement in CP, current status of outcome measurement in CP, and issues of understanding change in childhood CP.