Bone mass and appendicular bone loss rates were examined in a cohort of Japanese-American men. Across their age range (ages 61 to 82 years) bone mass steadily declined at the proximal and distal radius, and at the calcaneus. The cross-sectional reduction in bone mass was 3.5-6.3% per decade at the various sites. Longitudinal measurements of the same cohort indicated greater losses than suggested by the cross-sectional data, yet still less than 10% per decade. Linear trends of increasing loss rates with aging were significant at the calcaneus, and marginally significant at the radius sites. However, the oldest men in the cohort strongly influenced these trends. Men under age 75 had essentially constant annual rates of bone loss. The most elderly men had both the lowest bone mass and the greatest bone loss rates.