In order to study the effect of acupuncture stimulation on bone mineral density (BMD), using the ovariectomized (OVX) rat model, we assessed the degree of osteopenia by dual-energy X-ray absorptiometry, measured the level of locomotor activity using a metabolism measuring system, and performed histological studies of bone tissue. Twenty-four female Wistar rats (8 weeks old, 160 - 180 g)were divided into three groups. Rats in the OVX-A group underwent ovariectomy followed by acupuncture stimulation. The OVX rats in the Vehicle control group were not treated with acupuncture as a control. The rats in the control group received neither ovariectomy nor acupuncture. Acupuncture stimulation for 12 weeks in the OVX-A group inhibited the reduction in BMD of the femoral bones caused by ovariectomy. Moreover, in the two OVX groups, there was no clear difference in the level of locomotor activity between the active and resting phases prior to acupuncture stimulation in each rat, and the pattern of locomotor activity was irregular. After acupuncture stimulation of the OVX-A rats, the pattern of locomotor activity became diphasic with clear active and resting phases, as was observed in the Control group. On histological studies, the continuity of trabecular bone was maintained more favorably and bone mass was higher in the OVX-A group than in the vehicle control group. These results suggest that the increased locomotor activity that had been induced by acupuncture stimulation increased the BMD.