In a retrospective comparison study of rates of postnatal depression using two self-rating instruments, a significantly higher incidence of postnatal depression was found among subjects who had undergone Caesarean section than in those who had a vaginal delivery. The excess of cases of postnatal depression among the Caesarean subjects appeared to consist of a milder illness which started sooner after delivery. Following Caesarean section, there was a significant association between postnatal depression and general, but not regional, anaesthesia.