Psychological and psychiatric morbidity can be a major source of distress to terminally ill patients and their relatives and friends. A prospective study was carried out to determine the prevalence of undiagnosed depression in palliative care patients and to determine whether factors such as age, previous psychiatric history and perceived social support have any association with the development of depression when patients have advanced metastatic cancer. Patients aged between 18 and 70 years who had a prognosis of < or = 6 months and who were receiving palliative care only for advanced metastatic cancer were interviewed using the Present State examination interview and a semi-structured interview to determine social support, information needs and past psychiatric history. One hundred patients were recruited and the prevalence of depression according to International Classification of Diseases 10 criteria was 22%. Perceived informal social support and past psychiatric history were not associated with being a case of depression but perceived information needs had a weak association. Younger patients and patients with breast cancer were more likely to be identified as being cases of depression. Further research is necessary to explore the aetiology and outcome of depression in palliative care. A high index of suspicion for depression should be maintained for younger patients with advanced metastatic cancer.