This paper presents differences by age in health care spending by type of expenditure and by source of funds through 1978. Use of health care services generally increases with age. The average health bill reached $2,026 for the aged in 1978, $764 for the intermediate age group, and $286 for the young. Biological, demographic, and policy factors determine each age group's share of health spending. Public funds financed over three-fifths of the health expenses of the aged, with Medicare and Medicaid together accounting for 58 percent. Most of the health expenses of the young age groups were paid by private sources.