Medical errors are common and dangerous, estimated to cause over 400,000 deaths per year in the United States alone. The field of neurosurgery is not immune to these errors, and many studies have begun analyzing the frequency and types of errors that neurosurgical patients experience, along with their effects and causes. Fortunately, these data are guiding new innovations to reduce and prevent errors, like checklists, computerized order entry, and an increased appreciation for volume–outcome relationships. This article describes the epidemiology of errors, their classification, methods for identifying and discovering errors, and new strategies for error prevention.