Ultrasound is now in use by the authors for detecting intracranial hematoma and secondary induced cerebral changes of edematous states of injured brains. Clinical and experimental data of the authors on the ultrasonic attenuation of injured brains have revealed useful to detect appearing edematous states of cerebrum. The ultrasonic attenuation is observed on sampled thirty cases of acute head injuries in respect to changes of neurological and physical conditions. With the decrease of ultrasonic attenuation values there are cases of 46.7go with impaired clinical signs and with-7 db of attenuation decrease in mean value, and 16.6% of cases have shown improved neurological and physical signs. With the increase of ultrasonic attenuation values there are cases of only 8.7% with impaired clinical signs and with +4 db in mean attenuation value, and 56.7%o of cases have showed improved neurological and physical signs. Consequently it may be able to find the correlation between the ultrasonic attenuation and the neurological, physical signs. The decrease of ultrasonic attenuation is accompanied by symptoms of anisocoria , etc., i.e., signs of appearing edematous states of injured brains. Ultrasonic beams for measuring the attenuation have to pass through the brain substance in large amount with little interference, so it is ade