A combination of low bone mass and decreased bone quality underlies osteoporotic fracture. We used scanning acoustic microscopy, a nondestructive method for assessing bone elasticity at a resolution of about 60 microns, to estimate the quality of biopsied iliac bones. We compared the acoustic velocities and bone volumes among premenopausal normal (n = 10), osteoporotic (n = 20), and postmenopausal normal (n = 10) subjects, the latter age-matched to the osteoporotic subjects. The acoustic measurements were highly reproducible (coefficient of variation = 0.32%). Bone volume of osteoporotic subjects (BV/TV = 13.3%) was lower than that of premenopausal and age-matched normals (BV/TV = 22.8%, p = 0.0007; BV/TV = 24.8%, p = 0.0004, respectively). Acoustic velocity of osteoporotic bone was 6.2% lower than that of age-matched normal bone (p < 0.02), but 3.4% higher than that of bone from premenopausal normal women. The lower acoustic velocity of osteoporotic bone than that of age-matched normal subjects implies that osteoporosis involves altered tissue elasticity. However, the lowest acoustic velocities were measured in premenopausal normal subjects. This unexpected result may indicate a complex relationship between tissue level properties and fragility in bone.