This thesis examines the ways in which 'medical' concepts have been used in penal discourse since the middle of the nineteenth century. By doing this I have tried to contribute to our understanding of modern methods of penal control and modern penal rationalities. The thesis contains two case studies. The first study examines the uses which have been made of the terms 'inebriety' and 'alcoholism' within penal discourse and also examines what is meant by the term 'treatment' when it is used in the context of 'the "treatment" of inebriates'. The second study looks at various ways in which the terms 'moral insanity', 'moral imbecility' and 'psychopathy' have been employed in penal discourses.