34 lower limbs were obtained from 17 individuals aged 33 to 92 years. Measurements of ultrasound attenuation and velocity were made on the intact heels and at four sequential stages of dissection resulting in a core of trabecular bone. Measurements of Young's modulus, porosity, mean trabecular plate separation, mean trabecular plate thickness, and density were subsequently obtained on the bone cores. Soft tissue was found to have a significant but correctable effect on attenuation and velocity values. The effect of cortical bone was also significant, but could not be corrected for in a clinical situation. Measurement of ultrasound attenuation and velocity appeared to be a promising technique for the assessment of "bone quality" in the calcaneus when measurements were made on either the intact heel or specimens of trabecular bone. Ultrasound attenuation and BUA were significantly related to mean trabecular plate separation. A combination of attenuation and velocity parameters was found to provide a good estimate of trabecular Young s modulus, with 70 percent of the variation in modulus described by this linear model of in situ measurements and R² increasing to 0.81 for measurements made in the trabecular core alone. Experimental measurements of modulus, porosity, tortuosity, permeability, and pore size were used with Biot's theory to predict ultrasound velocity and attenuation due to internal losses resulting from the interaction of the bone and marrow components. While the Biot-type internal losses contributed only a fraction of the attenuation seen experimentally, the qualitative relationships found between attenuation and measures of porosity or pore size agree with those seen experimentally. When surface reflections from a Biot material, scattering, and internal losses due to bone and fat absorption were included in the model, the predicted attenuation was of the same order of magnitude as that obtained in the experiments. Surface reflection was the dominant mechanisms at 232 kHz, while scattering and absorption were hypothesized to be equally important at frequencies of 584 kHz.