Borderline personality has been, for many years, a discredited diagnostic concept. In 1979 a review of the literature concluded that its validity status was very uncertain. The authors have reviewed research conducted since then and discuss it in terms of the Robins & Guze (1970) criteria. In spite of existing unclear issues, the balance is tipping in favour of the validity of borderline personality, as diagnosed with new research criteria. This development is taking place in the context of a growing interest in the area of personality disorders.