The aim of this chapter is to set out the psychoanalytic ideas and clinical principles on which Brief Psychoanalytic Therapy is founded. Topics include the centrality of intersubjective knowledge, the pivotal notion of transference, and the various ways in which a patient may affect a therapist’s emotional state. The clinical issues addressed range from varieties of communication and defence, contrasts between paranoid-schizoid and depressive position functioning, and the roles of countertransference and containment in the therapeutic endeavor. Overall, the chapter is concerned with the developmental potential of a therapeutic relationship in which the therapist is emotionally available and able to reflect upon the patterns of relatedness that a patient attempts to introduce into the therapeutic relationship, in part to avoid states of mind that are painful or conflictual.