Ninety-two women and their first-born children took part in a longitudinal survey of maternal mental health. When the children were four years old, their mothers were interviewed by means of the Behavioural Screening Questionnaire, and the children's problems were rated by a psychiatrist, who was unaware of the mothers' psychiatric histories or of assessments of their current health. As expected, mothers who were concurrently depressed reported significantly more behavioural difficulties in their children. Marital disharmony during pregnancy and a history of paternal psychiatric problems were also associated with later childhood behavioural difficulties. Children who scored below average on the McCarthy scales of cognitive abilities were also reported by their mothers to have more behavioural problems, but the children's behavioural difficulties at four showed no clear links with post-natal depression.