Healthcare-associated infection is one of the major challenges to providing high quality health care. Policy makers in the United Kingdom are emphasising initiatives to increase compliance with hand hygiene protocols because most cross-infection occurs via hands. The contribution of the environment to risks of infection has received less attention, despite media reports of dirty hospitals. However, the environmental contribution may be greater than previously considered. Changes in the way health care is delivered, especially the movement of patients and staff between different hospitals and wards, may also contribute to the difficulty of controlling infection.