A new diagnostic category, borderline personality disorder, was included in the psychiatric classificatory system for the first time when it appeared in the DSM–III (American Psychiatric Association, 1980). However, the label, some of the associated concepts, and of course, the patients, have all been around for much longer. The contemporary concepts have two roots. The first is in the psychoanalytic literature: on the borderline between neurosis and psychosis. These patients are chronically unstable and impulsive, have difficulties in close relationships, and are prone to brief psychotic episodes. The second root is in the general psychiatric literature: on the border of schizophrenia. These patients are cold and aloof, with odd speech, depersonalisation and derealisation, and recurrent illusions. This dual origin will be reflected in the choice of papers and books.