The establishment and first 18 months of a psychiatric liaison service to a general hospital obstetric unit are described. The service was initially intended to predict antenatally those at risk of postnatal depression and to offer follow-up throughout pregnancy and in the postnatal period. However, a large proportion of referrals were of women currently unwell. Furthermore, postnatal follow-up in the community proved difficult. Referrals, diagnoses and disposal are analysed, leading to conclusions about the effectiveness and problem of such a service. The components of a comprehensive obstetric liaison provision are proposed, emphasising the need for strong community links built around a CPN service, allowing adequate postnatal psychiatric care.