Medical malpractice and the problems associated with it remain an important issue in the US medical community. Yet relatively little information regarding the long-term history of malpractice litigation can be found in the literature. This article addresses 2 questions: (1) when and why did medical malpractice litigation originate in the United States and (2) what historical factors best explain its subsequent perpetuation and growth? Medical malpractice litigation appeared in the United States around 1840 for reasons specific to that period. Those reasons are discussed in the context of marketplace professionalism, an environment that provided few quality controls over medical practitioners. Medical malpractice litigation has since been sustained for a century and a half by an interacting combination of 6 principal factors. Three of these factors are medical: the innovative pressures on American medicine, the spread of uniform standards, and the advent of medical malpractice liability insurance. Three are legal factors: contingent fees, citizen juries, and the nature of tort pleading in the United States. Knowledge of these historical factors may prove useful to those seeking to reform the current medical malpractice litigation system.