Mental illnesses associated with pregnancy and childbirth have been the subject of many studies in the last 25 years. Because of divergent criteria and definitions, few of these studies have been comparable. Major sources of confusion have been the lack of a proper definition of a postpartum mental illness, whether there is a specific psychosis occurring in the postpartum state, and to what extent the common factor, childbearing, influences the course. There has been a notable lack of control groups in previous studies, so that the postpartum patient was viewed without benefit of comparison with a comparable patient group. Adequate follow-up studies have been lacking, and there has been confusion about the role of toxicity in producing this illness. Design The present investigation was undertaken in an attempt to clarify various aspects of definition, incidence, pathology, dynamics, and prognosis of the postpartum mental illness. Its purpose is essentially an exploratory