The prevalence of cerebral palsy (CP) ranges from 1.5 to 2.5 per 1000 live births with little or no variation among western nations, although data from the Americas are sparse. Time trends in overall CP prevalence for the past 40 years are most notable for their stability, but a modest increase in prevalence probably occurred in the last decades of the twentieth century. European countries have pioneered the development of CP registries, and as a result, CP is a condition that is enumerated regularly in several parts of the world. The United States has no CP registries, although ongoing surveillance of CP, along with other developmental disabilities, is performed by the Centers for Disease Control and Prevention in metropolitan Atlanta.