The past few years have witnessed an upsurge in work on depression and physical illness. This has been coupled with renewed interest in the biological processes underpinning depression and exhortation of physicians to recognise and treat depression in their patients. There are many reasons why the study of depression and physical illness is important. First, there is growing evidence that depression and depressive symptoms are determinants of some types of physical pathology. The investigation of depression therefore contributes to knowledge about factors promoting disease development and illness progression in people with existing disorders. Second, depression is crucial to the everyday functioning and healthcare utilisation of people suffering from physical illnesses. Severe depression is a good indicator of whether daily functioning is likely to be impaired and whether there is an increased risk of suicide. Third, self-management is a central feature of many clinical conditions and disabilities. If depression impairs people's engagement in appropriate self-care, then the burden of distress and disability will be increased and the effectiveness of medical management may be compromised. Fourth, treating comorbid depression is likely to improve the wellbeing and quality of life of patients with physical illnesses, and this may have an impact on the severity and progression of underlying pathology. Bearing in mind the global burden of disease and predictions concerning the future high demands on healthcare systems attributable to depression [1], there is a pressing need to understand the relationship of depression with physical illness and disability.