In the USA, severe psychiatric illness after childbirth strikes one woman for every 1000 births, or about 3500 women each year. An unrecorded number of new mothers experience lesser degrees of postpartum illness, and two distinct forms of severe illness can be distinguished. One form, called postpartum psychosis, is an agitated, very changeable condition, often characterized by confusion, hallucinations, delusions and sometimes episodes of violent behaviour. The other condition, major postpartum depression, begins two or three weeks after childbirth, and is characterized by confusion, depression of mood, and often with exhaustion, headache and digestive upset. Mixtures of the two severe disorders occur frequently. This volume contains a number of essays which support the position that postpartum disorders are primarily organic and are mainly disorders of hormonal deficit. They develop as the endocrine system falls back from the hyperactivity of pregnancy toward or beyond the levels of the prior non-pregnant state. Tremendous therapeutic opportunities exist or are imminent for both the organic and the psychological components of postpartum mental illness.