The psychiatric state of 483 women was examined antenatally and at 3, 6, and 12 months postpartum. Comprehensive assessments were made of all women antenatally and of subgroups of the full sample postnatally. Psychiatric state was assessed using the General Health Questionnaire, the Present State Examination and the Montgomery and Asberg Depression Rating Scale. In terms of PSE criteria, the point prevalence of non-psychotic psychiatric disorder antenatally was found to be 6.0%; and postnatally it was estimated to be 8.7% at 3 months, 8.8% at 6 months and 5.2% at 12 months after delivery. These prevalence rates were compared to the rate in a general population sample of non-puerperal women and found to be no greater. In a subgroup of the full sample, the incidence of psychiatric disorder in the year following delivery was estimated to be 15.1%, which is close to a figure previously reported for women in the community. The onset of psychiatric disturbance was soon after delivery in most instances; and, for the majority, the episode of disturbance lasted for 3 months or less. The distribution of PSE Catego classes and syndromes among the antenatal and postnatal samples were found to be similar to those in the non-puerperal comparison sample. Thus, the prevalence, incidence, and nature of non-psychotic psychiatric disorder in the 12 months following delivery do not appear to distinguish it from such disorders arising at other times.