Bone is continuously remodeled during adult life with the resorption of old bone by osteoclasts and its subsequent replacement by osteoblast. Bone homeostasis is maintained by a balance between activities of osteoblasts and osteoclasts, but an imbalance between resorption and formation results in bone diseases including osteoporosis. Osteoblasts line up on the bone surface, especially regions of new bone formation, lay down bone matrix (osteoid) in orderly lamellae and induce its mineralization. Thus, the increased activity of osteoblasts is helpful to treat and prevent osteoporosis. In this study, we examined whether 80% EtOH extract of yukmijiwhang-whan is capable of affecting osteoblast proliferation using human osteoblast-like cell line, MG-63 and Saos-2. In an in vivo experiment, extract of yukmijiwhang-whan was administered for 9 weeks to ovariectomized (OVX) rats. At necropsy, uterus weights were measured, and trabecular bone areas (TBAS) of tibia and the sixth lumbar vertebra were measured by bone histomorphology. The maximum cell proliferation of MG-63 caused by extract of yukmijiwhang-whan at $5;{ imes};10^{-6};mg/ml$ was approximately 115% compared with control. In Saos-2, cell proliferation was approximately 145% of control at $5;{ imes};10^{-4};mg/ml$ and maximum alkaline phosphatase (ALP) activity was approximately 143% of control at $5;{ imes};10^{-5};mg/ml$. In animal study, however, the tibia and lumbar TBAS of the yukmijiwhang-whan group did not increased than the OVX control group. In conclusion, the 80% EtOH extract of yukmijiwhang-whan increased proliferation of osteoblasts but did not prevent bone loss in OVX rats.