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 phenomenon in detail and analyzes 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.