Objective: The effects of various hormone replacement therapies on bone mineral density after 2 years of treatment were evaluated in this study. Methods: A total of 138 patients treated with either conjugated equine estrogen or transdermal 17-p estradiol alone or in combination with medroxyprogesterone acetate or dydrogesterone had bone mineral density measurements of the first four lumbar vertebrae by using a Dual X-ray Hologic 1000 quantitative digital radiography densitometer. Results: After 2 years of treatment, a significant increase in spinal bone mineral density was found in all groups. No significant differences were found among 6 treatment groups. Conclusion: There were no differences between estrogen replacement therapies and combined hormone replacement therapies. Progesterone did not have any additional effect on bone mineral density.