Concern has been mounting about the health and welfare of people who provide informal care for family or friends with chronic illness. In particular, young and elderly people - vulnerable groups in their own right - may be carrying a heavy burden. The extent of the problem is not well known because estimates have been pieced together from ad hoc local studies and household sample surveys. These estimated that young carers in the United Kingdom numbered between 10,000 and 50,000, and that about one in 20 older people in Great Britain spent long hours caring for sick family members. In 2001, for the first time the decennial UK census asked the entire population about caring responsibilities and general self rated health. We analysed the answers to these two questions to explore carers' wellbeing.