For the purposes of this volume, what is meant by the "Kleinian tradition" is that clinical and theoretical orientation initiated by Melanie Klein, following on the work of Freud, but significantly developed by, in particular, Wilfred Bion, Herbert Rosenfeld, and Hanna Segal, and more recently by, amongst others, Betty Joseph, John Steiner, and Ronald Britton. The development of this line of thought is well summarized by Elizabeth Bott Spillius, (1988, 1994), and its major theoretical and clinical concepts are comprehensively described by Robert Hinshelwood (1989, 1994).

The central theoretical concepts that inform the work of those practising in the Kleinian tradition are that of unconscious phantasy (Isaacs, 1948; Klein, 1958), the paranoid-schizoid and the depressive positions (Klein, 1935, 1946), projective identification (Klein, 1946) -- especially as it has been developed by Bion and Rosenfeld to be understood as a form of communication (Bion, 1959; Rosenfeld, 1971) -- the centrality of the oedipal situation (Britton, 1992b, 1998; Britton, Feldman, & O'Shaughnessy, 1989) and the theory of the container and the contained (Bion, 1962).