In this book the authors explore current issues in the conceptualisation, assessment and treatment of antisocial personality. Consideration of two related constructs, psychopathy and sociopathy, is unavoidable given overlap in their meanings. The New Oxford Dictionary of English offers the following definition of 'antisocial': contrary to the laws and customs of society, causing annoyance and disapproval in others, e.g., aggressive and antisocial behaviour [1]. A person with antisocial personality is therefore one who both acts unlawfully or contrary to social norms and customs, and behaves in ways that others find objectionable. The dictionary defines a 'sociopath' as one with a personality disorder manifesting itself in extreme antisocial attitudes and behaviour.1 A 'psychopath' is defined as a person suffering from chronic mental disorder with abnormal or violent social behaviour. This latter definition perhaps reflects the common (layperson's) perception of the 'psychopath' as someone who is dangerous and mentally deranged. Implicit in these definitions is the idea that there exists a continuum of antisocial behaviour or 'antisociality', ranging from the obnoxious but relatively benign, through the more severe and disordered (sociopathy) to the extreme (psychopathy) characterised by abnormal or violent social behaviour. This idea of an antisociality continuum is reflected in contemporary usage of these terms"--