Abstract: A diagnostic method for determining in vivo mechanical strength and structural integrity of hard tissues such as bones, in a non-invasive and non-dramatic manner. The method separates ultrasound energy affected by surrounding soft tissues, and thus permits unbiased determination of ultrasound parameters that represent the hard tissues. The mechanical strength of hard tissues is then determined on the basis of the ultrasound parameters, including the amount of energy propagated, the velocity of the ultrasound and the degree of dispersion together with the characteristic response of the hard tissues.