This text comprises an introduction to major psychoanalytical concepts in Kleinian theory starting with the ideas formulated by Melanie Klein and extending them to those developed by her main followers. There are chapters focusing on: the psychoanalytic play technique, unconscious fantasy, paranoid-schizoid and depressive positions, envy and gratitude, oedipus complex, projective identification, internal obejects, symbolization, models of the mind, containment and transference. This text is part of the "Whurr Series in Psychoanalysis" which publish clinical and research texts of academic excellence in the field. Each title makes a significant contribution and the series is open-ended. The chapters of this text have been written by leading psychoanalysts: David Bell, Jill Boswell, Ronald Britton, Marco Chiesa, Betty Joseph, Ruth Riesemberg Malcolm, Hannah Segal, Elizabeth Bott Spillius, Priscilla Roth and Jane Temperley.