This is the original work on which Hans Eysenck's fifty years of research have been built. It introduced many new ideas about the nature and measurement of personality into the field, related personality to abnormal psychology, and demonstrated the possibility of testing personality theory experimentally. The book is the result of a concentrated and cooperative effort to discover the main dimensions of personality, and to define them operationally, that is, by means of strictly experimental, quantitative procedures. More than three dozen separate researches were carried out on some 10,000 normal and neurotic subjects by a research team of psychologists and psychiatrists. A special feature of this work is the close collaboration between psychologists and psychiatrists. Eysenck believes that the exploration of personality would have reached an advanced state much earlier had such a collaboration been the rule rather than the exception in studies of this kind. Both disciplines benefit by working together on the many problems they have in common. In his new introduction, Eysenck discusses the difficulty he had in conveying this belief to scientists from opposite ends of the psychology spectrum when he first began work on this book. He goes on to explain the basis from which Dimensions of Personality developed. Central to any concept of personality, he states, must be hierarchies of traits organized into a dimensional system. The two major dimensions he posited, neuroticism and extraversion, were in disfavor with most scientists of personality at the time. Now they form part of practically all descriptions of personality. Dimensions of Personality is a landmark study and should be read by both students and professionals in the fields of psychiatry, psychology, and sociology.