Dangerousness is a feature of life in modern industrial societies. The general public in these countries are at risk of suffering grave harm from other persons in a variety of ways. But what exactly constitutes "dangerousness?" Who is "dangerous?" Should there be special sentences for "dangerous" offenders? In 1976 the Howard League for Penal Reform convened a distinguished working party to review and report on the law and practice in relation to "dangerous" offenders. The concept of "dangerousness" in criminal justice had been for some years the focus in the United States of an impassioned controversy to which there existed no British counterpart. The working party set out to confront the fundamental issues raised in the American debate. They offer a uniquely comprehensive review of the wide-ranging arguments and present controversial proposals for reform which embody the principles on which, approaching the problem from a variety of very different points of departure, they achieved a broad agreement.