This analysis examines how shifts in the age distribution of the U.S. population, reflecting both the aging of the baby-boom generation and increased longevity, will affect demand for hospital inpatient services during the next ten years. Over that period, aging will drive about 0.74 percent annual growth in use of services. Aging's effect on inpatient demand varies by medical condition, with the highest rates of growth in services most used by elderly patients. Even for those services, however, aging is a much less important factor than local population trends and changing practice patterns attributable to advancing medical technology.