Quantitative ultrasound (QUS) is a recently developed technique for evaluating fracture risk that can assess both bone mass and architecture. Although numerous studies have shown that menopause is associated with accelerated loss of bone mineral density, there are only a few studies on the association of QUS parameter (stiffness index) with menopausal status, especially among Japanese population. We examined age-specific changes in stiffness index, and relation with age, body mass index (BMI) and menopausal status among 506 community-dwelling Japanese women aged 40-89 years. Mean age at menopause (standard deviation) among 459 women with natural menopause was 49.4 (4.0) years. Stiffness index significantly decreased with increasing age. Stiffness index among 80-89 years age group was 40% lower, compared with that of 40-49 years age group. The greatest decline among adjacent ten-year age groups in stiffness index (15%) was found between 40-49 and 50-59 years of age. Multiple regression analysis showed that menopause related with decreased stiffness index, independent of age and BMI. Our findings indicate that menopause influences loss of bone mass and induces deterioration of bone trabecular microstructure.