A review of the literature reveals how little has been published by psychoanalysts about the important subject of postpartum depression. This article offers a way of looking at the phenomenon from a transgenerational perspective. The concept of symbiosis is taken from the mother's point of view as well as from the baby's. It is defined as a delusional two-person fantasy of mutual dependence rather than as a normal phase of development. The analysis of a case of postnatal depression is presented to illustrate the clinical and theoretical implications of this viewpoint and how it was applied in treatment.