This is a preliminary report from a prospective study of the influence of psychosocial stressors on post-natal relapse in women at high risk of psychiatric disorder after childbirth. Forty-three index subjects with a previous history of psychosis or severe depression were compared with 45 pregnant control subjects without any previous psychiatric disorder. After delivery 51% of index subjects relapsed (RDC diagnoses): 28% were categorised as psychotic and 23% non-psychotic. All psychotic relapses were in women with a previous history of bipolar or schizoaffective disorder (46% of this subgroup). Only the non-psychotic post-partum relapses (mostly depressions) were associated with an increased likelihood of a severe life event in the 12 months preceding illness onset.