This study was designed to (1) test the preventive and therapeutic effects of acupuncture on osteopenia in ovariectomized (OVX) rats, and (2) assess whether treatment of different acupuncture points causes different effects on tibiae, femora or lumbar spines. Thirty-five female Sprague-Dawley rats were divided into four groups: Sham (sham-operated, non-acupuncture); Model (OVX, non-acupuncture); Acp-A [OVX, bilateral needling of points Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6)]; and Acp-B (OVX, bilateral needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23)). Operations were performed at 8 weeks of age, 1 week later the study was started and continued for 16 weeks. Ovariectomy resulted in decreased bone mineral density (BMD) compared to the sham group over time, and Acp-A tended to have higher BMD than the other OVX groups, especially for tibiae. In addition, the bone ash weight of the Acp groups tended to be heavier than the model group. Deoxypyridinoline, the urinary marker of bone resorption, also appeared to be decreased in both acupuncture groups. Similarly, microarchitecture and bone morphometry of lumbar vertebrae and tibiae, such as bone volume, trabecular thickness, trabecular number, mineralizing surface, bone formation rate, mineral apposition rate, number of nodes and number of node-terminus struts, also showed the same improvement in the acupuncture groups as compared to the model control group. Our findings showed that acupuncture may prevent the development of osteopenia in rats induced by ovariectomy. Needling of Tsu-San-Li (ST-36) and San-Yin- Chiao (SP-6) seems more effective than needling of P'i-Shu (Bl-20) and Shen Shu (Bl-23) in bone anabolic regulation.