The authors forecast that the Inland Southern California area (the southeastern-most part of the state) is likely to experience a 32 percent shortfall in the number of physicians who provide patient care (including medical residents and fellows) by the year 2020. The authors conclude that their results are sensitive to a variety of factors, including the accuracy of population projections. However, based on a single criterion-a projected shortfall in the physician supply necessary to meet the demand for physicians in the four-county Inland Southern California region — a case can be made to move forward with the University of California, Riverside, medical school proposal. Under scenarios of rapid population growth (especially growth that is more rapid than forecast by the California Department of Finance), a healthy economy, an aging population (i.e., a decline in the proportion of the population that is under age 15), the demand for physicians in Inland Southern California will exceed the supply if the recent trends underlying the authors’ supply model continue.