The Keystone ICU study, which nearly eliminated catheter-related bloodstream infections in intensive care units (ICUs) in Michigan, is a landmark achievement in the patient safety field. This controlled study, which attempted to replicate the Keystone study in 223 ICUs in England, yielded a surprising result: infection rates declined significantly in both control and intervention hospitals, likely reflecting secular trends in infection rates. The authors note the need for ethnographic studies to complement traditional clinical research in order to determine the reasons behind the success (or failure) of quality improvement efforts.