Epidemiology of cerebral palsy (CP) aims to describe the frequency of the condition in a population and to monitor its changes over time, and a guide to the management of patients. Classification of CP is an important step toward describing more homogenous subgroups of persons with CP. Several classifications exist based on neurological signs and topography, on motor function loss, associated impairments, severity of the clinical pattern and on the neuroimaging findings. Caution should be paid when interpreting changes in prevalence rates since factors that may influence these estimates are numerous. The diagnosis may be made in infants as early as 4 months of age through a combination of neurological examination, prenatal findings, recognition of clinical risk factors and neuroimaging findings. Over the last 20 years, various other screening tests, developmental and neurological examination methods have been developed. For the fourth edition, the chapter has been reviewed/revised by the Book Editor.