The follow-up studies of borderline schizophrenia, the borderline syndrome and borderline personality disorder are examined in the light of modern methodological demands. Few studies reach these standards. The outcome of borderline schizophrenia is variable and close to schizophrenia. Approximately 20% of the cases develop true schizophrenia over time. Grinker’s borderline syndrome has also a variable outcome but mostly a poor prognosis. Borderline personality disorder has a variable outcome but better than for schizophrenia. Concomitant major affective disorder is frequently present in borderline personality disorder and influences outcome. The wide range of outcome does not support a single ‘natural history’ of these disorders. Few predictive factors have been identified. Better studies with the aim of identifying predictive factors are mandatory.