Personality disorders related to schizophrenia were described since Kraepelin's works. According to the DMS III-R those disorders are gathered into the A cluster of personality disorders consisting in: schizotypal, schizoid and paranoid personality disorders. Schizotypal and paranoid personalities are biologically linked to schizophrenia and support the concept of "schizophrenia spectrum". Until now such a link is not found between schizoid personality and schizophrenia. Future research in the field of those personality disorders will bring a better knowledge in the pathogenesis of schizophrenia.