This paper explores factors that might be driving the significant variation in use of hospital beds by patients over 65 admitted as an emergency. It considers the contribution made by patient-based (demand-side) factors, hospital (supply-side) factors, the availability of community services and resources, and broader system relationships (how care systems and staff work together and relate to each other) in driving the observed variation in length of stay and rate of admission. Its conclusions are based on new analysis by The King’s Fund of Hospital Episode Statistics (HES) and local population -based data.