Partners and other family members are key supports for cancer patients. Most cope well with the caregiving role, but an important minority become highly distressed or develop an affective disorder. Female carers and those with a history of psychiatric morbidity are more vulnerable, as are those who take a more negative view of the patient's illness and its impact on their lives. Carers are likely to become more distressed and develop psychiatric morbidity as the illness advances and treatment is palliative. Carers are also more at risk when they lack a support network of their own and when there are relationship difficulties with the patient. The review discusses why, given this evidence, carers fail to take advantage of interventions designed to help them and those who participate derive only limited psychological benefits.