To evaluate the effects of alfacalcidol on bone turnover in elderly women with osteoporosis, an open-label, prospective, calcium-controlled study was conducted. A total of 80 patients with osteoporosis were divided into two groups: the control group, group C (mean age, 78.0 years), in which patients were given calcium, and group D (mean age, 77.4 years), in which the patients were given alfacalcidol 1 μg/day together with calcium for 6 months. Calcium regulation, lumbar bone mineral density (LBMD), and markers for bone turnover were assessed. A significant increase in urinary calcium/creatinine ratio (90% increase from baseline at 3 months; P = 0.0083, and 60% at 6 months; P = 0.0091) and a significant decrease in serum parathyroid hormone (30% decrease from baseline at 6 months; P < 0.0001) was observed in group D compared with the corresponding changes in group C. Significant decreases of bone resorption markers (deoxypyridinoline and N-telopeptide) at 6 months (about 15% decrease from the baseline values) were observed in group D compared with the corresponding changes in group C. The changes in bone formation markers (bone-derived alkaline phosphatase and osteocalcin) in group D were significantly different at 6 months (-21.5%; P = 0.0047 and -13.4%; P = 0.0032, respectively) from the values in group C. The magnitudes of the decrease in bone turnover markers were highly correlated with the corresponding baseline values, suggesting that alfacalcidol treatment effectively reduces bone turnover in patients with high bone turnover rates. The LBMD in group D increased by 1.7% and that in group C decreased by 1.6% (P = 0.0384). The changes in calcium metabolism and LBMD were in good agreement with those in previous reports. Although the changes in bone turnover markers in group D were slight, significant reduction in bone turnover with alfacalcidol treatment, together with the change in calcium metabolism, may account for the effects of alfacalcidol on BMD and on fracture prevention reported previously. In conclusion, alfacalcidol reduces bone turnover in elderly women with high-bone-turnover osteoporosis, and it may have beneficial effects on bone.