Expenditures for Medicare beneficiaries in the last year of life decrease with increasing age. The cause of this phenomenon is uncertain.To examine this pattern in detail and evaluate whether decreases in aggressiveness of medical care explain the phenomenon.Analysis of sample Medicare data for beneficiaries aged 65 years or older from Massachusetts (n = 34 131) and California (n = 19 064) who died in 1996.Medical expenditures during the last year of life, analyzed by age group, sex, race, place and cause of death, comorbidity, and use of hospital services.For Massachusetts and California, respectively, Medicare expenditures per beneficiary were $35 300 and $27 800 among those aged 65 through 74 years vs $22 000 and $21 600 for those aged 85 years or older. The pattern of decreasing Medicare expenditures with age is pervasive, persisting throughout the last year of life in both states for both sexes, for black and white beneficiaries, for persons with varying levels of comorbidity, and for those receiving hospice vs conventional care, regardless of cause and site of death. The aggressiveness of medical care in both Massachusetts and California also decreased with age, as judged by less frequent hospital and intensive care unit admissions and by markedly decreasing use of cardiac catheterization, dialysis, ventilators, and pulmonary artery monitors, regardless of cause of death. Decrease in the cost of hospital services accounts for approximately 80% of the decrease in Medicare expenditures with age in both states.Medicare expenditures in the last year of life decrease with age, especially for those aged 85 years or older. This is in large part because the aggressiveness of medical care in the last year of life decreases with increasing age.