Paranoia is the suspicion that other intend to cause you harm. It is a common experience in the general population, though often overlooked. In its most severe form, paranoia occurs as persecutory delusions. Paranoia, written by leading researchers in this field, is the first cognitive psychology book to have persecutory delusions as its focus. Scholarly, comprehensive and illustrated by clinical examples throughout, this study defines the phenomena in detail and analyses the content of persecutory delusions. It reviews previous psychological writings, explores the relationship between psychosis and neurosis, reports on innovative empirical studies with patients, and highlights future essential research directions. Paranoia outlines a new theoretical model of the formation and maintenance of persecutory delusions, providing an excellent guide to this important clinical topic. It will be of great interest and use to all psychiatrists and clinical psychologists who work in this field.