In order to study the effect of acupuncture stimulation on bone mineral density (BMD), using theovariectomized (OVX) rat model, we assessed the degree of osteopenia by dual-energy X-rayabsorptiometry, 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 ovariectomyfollowed by acupuncture stimulation. The OVX rats in the Vehicle control group were not treatedwith acupuncture as a control. The rats in the control group received neither ovariectomy noracupuncture. Acupuncture stimulation for 12 weeks in the OVX-A group inhibited the reductionin BMD of the femoral bones caused by ovariectomy. Moreover, in the two OVX groups, therewas no clear difference in the level of locomotor activity between the active and resting phasesprior 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 diphasicwith clear active and resting phases, as was observed in the Control group. On histological studies, thecontinuity of trabecular bone was maintained more favorably and bone mass was higher in the OVX-Agroup than in the vehicle control group. These results suggest that the increased locomotor activity thathad been induced by acupuncture stimulation increased the BMD.