It is uncertain whether or how rapidly elderly women continue to lose bone with advancing age. To determine rates of change in bone mass at the hip and at the calcaneus in elderly women and to compare these rates of change among estrogen users and nonusers, we prospectively measured rates of change in bone mineral density (BMD) at the total hip and its four subregions (mean ± SD, 3.55 ± 0.29 years between examinations) and at the calcaneus (mean ± SD, 5.69 ± 0.33 years between examinations) in 5698 community-dwelling white women aged 65 years or older at the baseline examination. The rate of decline in total hip BMD steadily increased from 2.5 mg/cm²/year (95% confidence interval 2.0 to 2.9) in women 67–69 years old to 10.4 mg/cm²/year in those aged 85 or older (95% confidence interval 8.4 to 12.4). The rate of bone loss also increased with aging at all subregions of the hip and at the calcaneus. The average loss of bone from the total hip is sufficient to increase the risk of hip fracture by 21% per 5 years in women aged 80 years or older. Compared with nonusers, current estrogen users had a 33% lower age-adjusted mean rate of loss at the total hip (2.9 vs 4.3 mg/cm²/year, p ≤ 0.0001) and a 35% lower age-adjusted mean rate of loss at the calcaneus (3.9 vs 6.0 mg/cm²/year, p ≤ 0.0001). The rate of bone loss in the hip and calcaneus steadily increases with advancing age in older women. Estrogen therapy may significantly decrease this loss. Efforts to understand and prevent bone loss should include elderly women.