This paper projects the use of medical care forward and backward, from 1950 to 2050, to show the importance of the changing age structure of the population for this sector of the economy. The results indicate that institutional care will consume a growing share of the medical care budget in the next century. If rates of use by age and sex remain at current levels, the aging of the population will push days of hospital care to 1621 per 1000 population in 2040, the peak year for hospital use, compared with 1241 per 1000 in 1975. Residents in nursing homes are projected to number 12.8 per 1000 population in 2050, almost two-and-one-half times the 5.4 per 1000 of 1975. Outpatient visits to doctors and visits to dentists are largely unaffected by age structure.