BACKGROUND The course of postnatal depression was examined in first-time mothers and fathers with emphasis on the role of personality and parental relationships as risk factors. METHODS 157 couples were assessed at four points: antenatally and at 6, 12 and 52 weeks postnatally. Various measures of mood and personality were administered at each of these assessment points. RESULTS Examination of the factors associated with depressed mood suggested that a woman's relationship with her own mother was important in the early postpartum stage, and also her level of interpersonal sensitivity and neuroticism. For the father, his relationship with either his mother or father and his level of neuroticism were associated with his mood level early on. By the end of the first year couple morbidity increased, with rates of distress being at their highest for both parents, and factors associated with depressed mood being linked to partner relationship variables, at least for mothers. At most time points, antenatal mood and partner relationship were significant predictor variables for the postnatal mood of both mothers and fathers. CONCLUSIONS The sample had a relatively high level of education and this should be taken into account when considering the generalisation of findings to less educated populations. At the time of conducting this study, the Edinburgh Postnatal Depression Scale (EPDS) had only been validated for use in the first few months postpartum, and thus we used another scale to measure the mother's mood at the other assessment points (the Beck Depression Inventory). Current research would suggest that the EPDS is valid both antenatally and at other times in the first year postpartum. CONCLUSIONS Whilst there was some consistency for mothers and fathers in the variables that predict their postpartum adjustment, these being antenatal mood and partner relationship, there is also evidence that adjustment to parenthood was related to different variables at different times. Early adjustment was related to the couple's relationship with their own parents, as well as their own personality. Later adjustment was related to the couple's functioning and relationship.