Twenty-six women with a history of bipolar or schizoaffective disorder, 17 women with histories of major depressive disorder and 45 control women without any previous psychiatric history were assessed in the 9th month of pregnancy on selected psychosocial measures. No subject was a 'case' as defined by the Research Diagnostic Criteria (RDC) from this time until the delivery. Within 6 months postpartum, 22 (51%) of the women with histories of mental illness were categorised as having relapsed (RDC case). Twelve women developed a psychosis (mania, hypomania or schizomania) and these illnesses occurred only in women with histories of affective or schizoaffective psychosis whereas 10 other women who became depressed after delivery came equally from the women with histories of psychosis (N = 5) as from those with histories of major depression (N = 5). Three (7%) control women also developed postpartum non-psychotic depressive disorders. Multivariate analyses suggest that different psychosocial factors contribute to the recurrence of affective and schizoaffective psychosis after delivery as opposed to non-psychotic postpartum affective disorders. A non-psychotic illness was predicted by antenatal neuroticism and a severe life event before illness onset. A recurrence of psychosis postpartum was predicted by a history of mania, hypomania or schizomania, a more recent psychiatric admission and reported marital difficulties. In this sample of women, life stress led to postpartum depression irrespective of the subject's past history and the high rates of recurrence of affective or schizoaffective psychosis (47%) probably mainly reflected a pre-existing physiological or psychological vulnerability which may have been exacerbated by, or contributed to, marital difficulties.