In fall 1997, a shortage of intravenous immunoglobulin (IVIG) developed in the United States because of increased demand for the product, reduced supply,and product recalls. This shortage is a useful model for understanding how our health care system responds to scarcity. Although the U.S. government took steps to inform the medical community of the shortage, with few exceptions,the government did not respond to the shortage in a timely or effective manner. Instead, it took a relatively passive role, leaving IVIG manufacturers and distributors, health care institutions, and clinicians to fend for themselves. The shortage likely had an uneven impact on patients, based on the relative market strength of the health care institutions in which they received care and the individual patient's ability to absorb the increasing out-of-pocket costs of scarce IVIG. Market mechanisms have now largely alleviated the shortage and significantly reduced its detrimental impact on patients. However, future shortages of IVIG or other scarce medical products,such as vaccines and antibiotics, would benefit from more immediate and coordinated efforts not only to make sure that scarce health care resources are distributed in a just manner but also to identify and remedy the sources of health product supply problems.