Medical errors account for ∼98,000 deaths per year in the United States. They increase disability and costs and decrease confidence in the health care system. We review several important types of medical errors and adverse events. We discuss medication errors, healthcare-acquired infections, falls, handoff errors, diagnostic errors, and surgical errors. We describe the impact of these errors, review causes and contributing factors, and provide an overview of strategies to reduce these events. We also discuss teamwork/safety culture, an important aspect in reducing medical errors. © 2012 by Annual Reviews. All rights reserved.