The discussion uses the prosecution function as the unit of analysis and concludes that changes in prosecutorial systems in the United States and other countries are part of a trend toward increasing rationality that is occurring in many other areas of modern society. The analysis traces three major stages in the development of prosecution systems. The first is associated with the emergence of true criminal law and occurred with the transition from societies in which almost all wrongs were regarded as private matters to societies in which wrongs came to be viewed as harmful to the community. The second stage lasted for centuries and entailed the growth and experimentation involving a variety of institutions and procedures. During this period the accusatorial and inquisitorial systems emerged. The third and most recent stage has involved governmental regulation of the volume and mix of cases processed by the criminal justice system to conserve resources and target selected aspects of crime. Chapter reference notes