Postnatal depression is a major public health problem affecting about one in seven women after childbirth. Depression is also common during pregnancy and throughout the perinatal period it is associated with symptoms of anxiety. Apart from the adverse consequences for women themselves becoming depressed when they are going through demanding physical and social changes, there are additional concerns. There is the possible negative impact of maternal depression on the relationship between mother and child and on the child's emotional, behavioural and cognitive development. Primary prevention and early intervention/secondary prevention strategies are potentially important in view of the frequent contact pregnant women, new mothers and infants have with health services, but the effectiveness of these strategies needs to be tested. In the past year there have been five new studies of antenatal screening for postnatal depression. These studies are consistent with nine earlier studies in showing that there is no evidence to support routine antenatal screening for postnatal depression. Seven new primary prevention/early intervention trials add evidence on a wide range of interventions ranging from practical support to individual interpersonal therapy, but without identifying significant differences in depression as an outcome. Two new trials of secondary prevention, one involving interpersonal therapy and the other including partners in a series of psychoeducational visits, show promise but neither is large enough to form a basis for practice change. Novel interventions, or promising findings, with a strong basis in theory need to be tested in trials which are appropriately sized and which comply with internationally accepted design and reporting guidelines.