The natural frequency of bone is studied in normal and fractured bones, in vitro as well as in vivo, by recording the outputs of microphone pick-ups, attached at proximal and distal ends to the bone defect. Natural frequency of bone is determined for an optimum output displayed on a cathode ray oscilloscope with respect to different stress wave frequencies. A comparative study of normal and fractured bone in vivo in 25 patients was made to diagnose the size of the fracture and its rate of healing. The natural frequency and intensity of sound in the injured bone was reduced while the output voltage increased with respect to the normal bone. The investigation reports a simple, reliable and rapid technique for the assessment of bone fracture.