A discussion on personality disorders (F6) is conducted within the framework of the Research Criteria Study on the basis of one case each of borderline syndrome (F60.31), transsexualism (F64.0), and factitious disorder (F68.1). In the Research Criteria Study the main agreement achieved about personality disorders was 77%, for borderline disorders 94%, transsexualism 91%, and factitious disorders 53%. Additional diagnoses were given in the case of factitious disorder by 43%, for borderline disorders in 15%, and for transsexualism in only 3%. Alternative diagnoses improved the overall agreement about factitious disorders by 21%, about borderline disorders and about transsexualism by 3%. It appears justified to introduce a coding for an alternative main diagnosis. The diagnostic concepts are discussed with respect to practicality, suitability, adequacy and reliability. The raters felt fairly secure about the classification. The research diagnostic criteria proved to be very practical. The raters attributed a high reliability to ICD-10 and, with the exception of factitious disorders, a very valid image of patients.