In virtually every community in this nation, the emergency department (ED) is an integral part of the health care safety net, often serving as the only available point of access to the health care system for many vulnerable and disenfranchised individuals. The authors present a brief overview of the March 2000 report released by the Institute of Medicine that described and assessed the current status of the nation's health care safety net. The authors discuss the role of the ED as a safety net provider and as a window onto the status of the rest of the health care system. The authors describe the Andersen behavioral model of health services use and suggest it as a useful theoretical framework for emergency medicine researchers who are interested in studying these issues.