This study of the history of British bad girls uses a wide range of professional, popular and personal texts to explore the experiences of girls in the twentieth century juvenile justice system. It examines the processes leading to their definition as variously delinquent, defective or neglected and analyses the different possibilities for public and private reform available to them. It shows how bad girls , though few in number, posed a recurring challenge to established generational and gender orders and questions the popular contemporary belief that rising delinquency among girls has been the product of late-twentieth century social changes.