Book excerpt: Can severe mental illness be prevented by early intervention? Mental illness is highly prevalent in the general population and has its onset mostly in adolescence and young adulthood. Early intervention usually leads to improved prognosis. This book describes a newly developed, evidence based cognitive behavioural intervention that can be used by clinicians to treat the precursor symptoms of psychosis and other severe mental illness. CBT for those at risk of a First Episode Psychosis offers a detailed new psychotherapy that has been shown to reduce the chance of transition to a first psychotic episode and to improve the chance for recovery. This encompasses: Psycho-education about prepsychotic symptoms A review of literature about psychological processes that are known to play a role in the development of psychosis A comprehensive manual – illustrated by numerous clinical vignettes - that can be used to treat help-seeking subjects with an increased risk of developing psychosis. Links to online resources and exercises to be used in therapy and education. A description of the multicentre randomized clinical trial investigating this new psychotherapy. The vast collective experience and expertise of the authors of this handbook results in an invaluable text for clinicians working in mental health care, as well as students, lecturers and researchers who have an interest in the prevention of schizophrenia and other severe mental illness.