Forty-six inpatients were independently diagnosed according to the DSM-III concept of borderline personality disorder, the diagnostic interview for borderlines (DIB) and the concept of borderline personality organization, which is linked to Kernbergs structural interview. The interviews were videotaped. Satisfactory inter-rater reliability was demonstrated for the DIB, which furthermore showed high sensitivity and specificity in identifying patients with a clinical DSM-III diagnosis of borderline personality disorder from patients with a other personality disorders or schizophrenic disorders. Discriminant features, demographic profile and earlier treatment history for the patients with a borderline personality disorder are described and discussed. The structural interviews were scored according to a specified format. Inter-rater reliability was satisfactory but not too impressive. Borderline personality organization turned out to be a very broad concept and only half of the patients within this concept received a syndrome diagnosis of borderline personality disorder. A general conclusion was that borderline personality organization should not be considered as a diagnostic entity but rather as a different diagnostic dimension representing an intermediate level of personality structure.