United States national data were used to assess factors responsible for the increase of brain tumor mortality. Between 1968 and 1988, death rates increased 50% among those aged 65-74 years, 200% among those aged 75-84 years, and 800% in the oldest old. Rate of increase and maximum death rate have changed over time. Death rate among the population aged 65-74 years peaked in the mid-1980s, while among those aged 85 years and older it is projected to continue increasing throughout the 1990s. The patterns of rate increases were almost identical in the two sexes, as well as among whites and nonwhites. There was a strong correlation over time of death rates with head diagnostic procedures (r = 0.96) and with the pace of computerized axial tomography installation (r = 0.91). The authors conclude that the reported increase in brain tumor mortality is not genuine, but represents a combination of three factors: availability of more sophisticated, noninvasive diagnostic technology; change in the attitude toward care of the elderly; and introduction of support programs such as Medicare that facilitate diagnostic procedures in the elderly.