Postnatal depression (PND) is a serious and debilitating condition that disrupts women's lives at a time when they are already under stress, adapting to the substantial demands having a baby creates. PND is linked with adverse effects on the development of the child and the family system, including poor marital adjustment and elevated levels of depression in male partners. Implications, not only for men's health, but also for the amount and quality of support men can provide for their partners and children are far-reaching. Preventative programmes for the treatment of PND have been widely advocated, but are rare in the literature. Even fewer, are treatment programmes that include male partners. This study compared the efficacy of a structured Cognitive Behavioural Therapy (CBT) programme for the treatment of PND, delivered in 3 different ways, within an Australian semi-rurallcoastal community. Thirty-nine women, diagnosed with PND, completed 10 weeks of either 'individual' (n=9), 'group women only' (n=16) or 'group partners involved' (n=14) intervention and were compared with a control support group (n=7). Pre-intervention, women in the study reported the presence of a number of psychosocial risk factors for PND and almost 20% of the men in this sample were also depressed according to the BDI-II. Partners of the women in the 'group partners involved' treatment completed a 6-week CBT group programme especially designed for men (n=13). Partners of the women involved in the other interventions acted as a control group (n=16). Depression, anxiety, parenting stress, relationship adjustment and social support measures were taken using standardized instruments at pre-intervention, post-test and at 3- and 6-month follow-up. Qualitative information about the experiences of PND and the intervention programme was obtained through focus group interviews. The intervention programme was evaluated by questionnaire by both participants and their general practitioners or allied health professionals who had referred them to the programme. Results indicated that, overall, the 10-week, structured CBT programme was far more effective in treating PND than attending a support group. Over time, group therapy outperformed individual therapy for depression and anxiety. Including partners in intervention meant significantly improved outcomes at 6-month follow-up for depression, anxiety and relationship adjustment for women. When male partners were included, women's social support levels were significantly higher at 3-month follow-up. Post-intervention men who participated in the men's group were significantly less depressed and stressed, and showed higher levels of social support than controls. The intervention programme was rated highly by both participants and referrers for effectiveness and acceptability, with the psychoeducational information and CBT strategies rated as the most useful components. Participants viewed the inclusion of male partners in PND treatment as fundamental and strongly recommended increased community and professional awareness of PND and its consequences. The important implications for clinical practice and resource allocation raised by this study are addressed.