The author presents a comprehensive re-evaluation of the concept of paranoia in the light of the broad conceptual spectrum involved. Beginning with the formulations of Melanie Klein, he examines the ideas of Freud and major analysts and psychiatrists who have dealt with this topic. Except for some distortions of analytic views he presents an interesting attempt to delineate the central core which allows for such differences in clinical manifestations as characterological bent, megalomania, benign outside influences, and malevolent persecution. He sees this core as consisting of feelings of unworth and insignificance, the incapacity for self-referral of responsibility, the inability to tolerate ambivalence, and especially the insistence on being overwhelmingly important to others. He does not see as essential the defense against homosexual impulses.