A representative sample of 105 women were assessed by Goldberg's Standardised Psychiatric Interview (SPI) on two occasions during pregnancy and twice more in the puerperium. Total SPI scores increased significantly after childbirth. Thirteen of the sample had a severe postnatal depression and a further 17 women had milder depression, which in 15 lasted at four weeks. Marked deterioration of their martial relationships was reported by the depressed women but no other social or obstetric characteristics of postnatal depression were found. Women with severe postnatal blues were particularly at risk of developing persistent depressive symptoms subsequently. The only two women referred to a psychiatrist had personality disorders rather than depressive illnesses.