Health and social outcomes in children who have cerebral palsy (CP) depend on several factors, including the severity of the CP, medical interventions, and the child's environment. One of the hallmarks of cerebral palsy is its variability. Several formal methods of classifying persons with CP, such as the Gross Motor Function Classification System, have been developed to standardize that variability. Children and adults with CP must contend with increased mortality as well as many secondary conditions that can affect activities and participation in society. Predicting outcomes for children with CP, establishing realistic goals, and determining the best interventions to improve functioning are facilitated by applying research results to individual decisions. Many more such studies are needed—especially those performed with large representative samples. In addition, the childhood factors that affect outcomes in adults with CP still need to be elucidated.