Previous articles in this series have investigated the role of human factors engineering (HFE) in the design and development of medical devices and instrumentation. This article turns its focus to HFE within health care facilities--hospitals, clinics, nursing homes, HMOs, etc. The objective of HFE for the device manufacturer is to produce effective and safe systems. The health care facility is concerned with maintaining the safety of patients and staff, enhancing the cost efficiency of its operations, and controlling liability. Human factors engineering can be effective in realizing all of these goals. Proactive measures include (1) evaluation of currently employed systems for efficiency and error potential, (2) evaluation of systems prior to purchase, (3) evaluation and enhancement of facilities, and (4) design and evaluation of procedures. Retroactively, HFE participation in accident/incident investigations can carry such investigations beyond the placing of blame to determining what made a human error possible or even inevitable.