OBJECTIVE: To estimate the current incidence and prevalence in the United States of 12 neurologic disorders. METHODS: We summarize the strongest evidence available, using data from the United States or from other developed countries when US data were insufficient. RESULTS: For some disorders, prevalence is a better descriptor of impact; for others, incidence is preferable. Per 1,000 children, estimated prevalence was 5.8 for autism spectrum disorder and 2.4 for cerebral palsy; for Tourette syndrome, the data were insufficient. In the general population, per 1,000, the 1-year prevalence for migraine was 121, 7.1 for epilepsy, and 0.9 for multiple sclerosis. Among the elderly, the prevalence of Alzheimer disease was 67 and that of Parkinson disease was 9.5. For diseases best described by annual incidence per 100,000, the rate for stroke was 183, 101 for major traumatic brain injury, 4.5 for spinal cord injury, and 1.6 for ALS. CONCLUSIONS: Using the best available data, our survey of a limited number of disorders shows that the burden of neurologic illness affects many millions of people in the United States.