BACKGROUND: In postmenopausal women, progestogen should be added to protect the endometrium from hyperplasia or carcinoma induced by the unopposed estrogen. However, the effects of progestogen on bone mineral densities and serum lipodproteins have not been precisely evaluated in Korean postmenopausal women. METHODS: To evaluate the effects of progestogen on bane mineral densities and serum lipoprotein in estrogen rephcement therapy, we canducted a 2-year trial of long conjugated equine estrogen(conjugated estrogen 0.625mg/day) with or without cyclic progestogen(MPA 5mg/day for 12 days) in 120 postmenopausal women. In all subjects, bone mineral density was measured in lumbar vertebra(L2-L4) and femur neck using dual energy X-ray absorptiometry(DEXA) and serum lipoprotein was measured from the beginning of the treatment, 12 manths, and 24 manths later, respectively. RESULTS: BMD of femur neck in both groups increased but not significantly compared to basal level at 12 months and/or 24 months of treatment. As for BMD of lumbar spine, it increased significantly in both groups. Both groups showed a significant decrease in the levels LDL cholesterol, but there was no statistical significance in serum triglycerids. Conjugated estrogen plus MPA group in constrast to conjugated estrogen only group showed a significant decrease in total cholesterol levels. CONCLUSIONS: These results suggest that the addition of MPA of the daily of 5mg for 12 days cyclically in estrogen replacement treatment appear to be effective in postmenopausal women with protection on bone mineral density and maintenance of long-term favorable effects on serum lipoprotein.