We studied the effects of soy isoflavone supplements on bone metabolism marker (serum osteocalcin, urinary deoxypyridinoline) and urinary mineral excretion (urinary Ca, Mg, Zn) in 47 postmenopausal women. There were 24 participants in the treatment group and 23 in the control group. The treatment group consumed isoflavone extract capsules daily (which contained 90 mg of soy isoflavones) for 12 weeks. The study compared before and after isoflavone intake in the following areas: Physical examination, diet survey, bone metabolism marker and urinary mineral excretion. The average age of the treatment group was 64.6 years and that of the control group was 66.5 years. There were no significant differences between the two groups in terms of height, weight and body mass index. Both groups maintained a regular diet pattern in terms of their average daily nutrient intake. There were no significant differences between the treatment group (23.9 mg) and the control group (25.4 mg) in terms of daily isoflavone intake based on diet. The analysis of bone metabolism marker changes in the treatment group after 12 weeks of taking the isoflavone supplements demonstrated significant differences in the following: Serum osteocalcin (13.7 ng/mL in befor versus 6.8 ng/mL in after) and urinary deoxypyridinoline (5.9 nmol/mmol Cr in befor versus 4.5 nmol/mmol Cr in after). The subjects in the treatment group showed no significant difference in urinary Ca excretion. But the subjects showed a significant difference in urinary Mg (131.9 mg/day in befor versus 115.6 mg/day in after) and Zn (400.5 $mu extrm{g}$/day in befor versus 310.2 $mu extrm{g}$/day in after) excretion in the isoflavone treatment group at the levels of p<0.001, p<0.01, respectively. No changes were made in the intake of minerals. The composition of serum osteocalcin and urinary deoxypyridinoline, and indicators of bone metabolism, including the excretion Mg and Zn, significantly decreased. As a result, bone mineral loss was lessened. (Korean J Nutrition 36(5): 476~482, 2003)