BACKGROUND: Hormone replacement therapy (HRT) has been used as a effective therapeutic strategy of postmenopausal osteoporosis. However, the studies on HRT are insufficient, particularly in early postmenopausal women in Korea. This study was designed as a community based clinical trial and was conducted for 1 year. METHODS: One hundred and forty early postmenopausal women aged 49 to 54 years who resided in Ulsan in Korea were enrolled in this study. The osteoporosis prone life style and general characteristics of the participants and their measured BMD were investigated. The therapy groups included 45 women who were assigned to one of the following regimens in 28 day cycles for 1 year: (1) conjugate equine estrogen (CEE), 0.625 mg/d daily, medroxyprogesterone acetate (MPA) 2.5 mg/d daily and calcium 500 mg/d daily (2) CEE 0.625 mg/d daily, MPA 10 mg/d for days 1 through 12 and calcium 500 mg/d daily. RESULTS: The women in the therapy groups had an average gain of 5.4%, 4.2%, 2.1%, 4.9% in BMD in the lumbar spine, femur total, femur neck and ward's area, respectively. HRT has significantly influenced the BMD after controlling age, month since menopause, alcohol intake, smoking, calcium intake, exercise, body mass index and baseline BMD. The baseline BMD and the BMI were factors that influenced the effect of HRT in BMD. CONCLUSION: HRT had positively influenced the BMD in Korean women. The baseline BMD and the BMI were predictors of the effect of HRT in BMD change.