To prove the existence of a current anesthesiologist shortage, and to project the balance of labor supply and demand in the future. To quantify the current supply we used published health personnel data from federal agencies and the American Medical Association, as well as membership data from the American Society of Anesthesiologists. We estimated anesthesiologist supply in 2001 based on the number of graduating residents and fellows, taking into account the loss of a portion of graduating residents due to temporary visa status. We assumed that neither a shortage nor an oversupply existed in 1994 and that demand for anesthesiologists was approximated by the number of surgical procedures reported by federal agencies. In modeling future supply and demand for anesthesiologists, we assumed that the current health care policy and economic climates will continue. We extrapolated demand using 1.5% to 3% yearly growth rates based on a synthesis of recent and projected procedure growth rates, procedure rates for the elderly, and population aging trends. We estimated the supply for 2001 through 2003 based on the current resident cohort modified by their projected graduation rate. Accounting for attrition during residency and the effect of fellowship training, we assumed that after 2003 the number of American medical graduates will initially increase by 15% annually and that the number of international medical graduates will decrease to a stable level of 500 trained each year. We assumed an average retirement age of 65 years. Our model suggests that there is currently a 3.6% to 10.9% shortage of anesthesiologists nationwide, depending on the assumption of a 2% or 3% increase in annual demand since 1994 and a constant pattern of work distribution by anesthesia providers. This amounts to approximately 1200 to 3800 anesthesiologists. If projected demand continues to increase at the rate of 1.5% to 2% annually, the shortfall will amount to 2.6% to 12.0% of the labor supply by 2005, representing a deficit of 1000 to 4500 anesthesiologists. By 2010, this shortfall is projected to disappear or continue to amount to about 11% of the anesthesiologist supply, depending on the assumptions about the rate of demand for anesthesiologists. Compared with the expected graduating class of 1100 anesthesiology residents in 2001, our model calls for nearly 1600 graduates by 2005 and 2000 by 2010. A substantive shortfall of anesthesia personnel exists in 2001 and will continue for years to come, fueled by changing population demographics, population health trends, and accelerating advancements in surgical technology, as well as growth in ambulatory and office-based surgery, pain medicine, and intensive care. In addition to focusing on financing, national health policy needs to address the adequacy of health care personnel resources for an aging population, in particular when they require surgery, are afflicted by painful conditions, or become critically ill.