Bone mineral density (BMD) at the distal one-third of the radius bone was measured by the dual energy X-ray absorptiometry (DEXA) method and cytoplasmic free calcium concentration ([Ca²⁺] _i) of urinary granulocytes was by flow cytometry. Enrolled in this investigation were healthy aged people (male: n=34, female: n=36, mean 74.4 yrs) in a rural area of southern Nagano prefecture. We used acetoxymethyl ester of fluo-3 (fluo-3AM) to measure [Ca²⁺]_i, in human urinary granulocytes. BMD of the male population (0.67g/cm²) was higher than that of the female population (0.47g/cm²).[Ca²⁺] _i, of urinary granulocytesin the female population (78.7nM) was higher than in the male population (48.2nM).[Ca²⁺] _i, in urinary granulocytes of the aged population was 63.5±51.2nM (mean±SD). These values were within the values of healthy adult peripheral blood cells, suggesting that these granulocytes were functional like blood cells. These data indicated that [Ca²⁺] i, of urinary granulocytes increased when BMD decreased, suggesting that the measurement of [Ca²⁺] _i, would give us a clue for the understanding of the pathophysiological mechanism of osteoporosis in the aged.