We project physician costs for the year 2,000 under several alternative scenarios, using different assumptions about the future supply of physicians and gross income (or expenditures) per physician. The supply of active, posttraining patient-care physicians is projected to increase from a ratio of 144 per 100,000 population in 1986 to 176 per 100,000 in 2,000. Depending on whether expenditures per physician increase at the rate of the consumer price index, the gross national product, or the historical 1982 through 1987 expenditure trends, there will be an additional cost (in constant 1986 dollars) of $21 billion, $30 billion, or $40 billion, respectively, compared with projected physician costs under a scenario of a constant physician-to-population ratio. The disproportionate growth of costs for practice overhead will pose a particular problem for efforts to restrain inflation of expenditures per physician.