SummaryA short review of some physical properties of ultrasound is presented, and their importance for echoencephalographic examinations is discussed.Calculations made on the basis of data concerning adult tissues, given by other authors, show that:A short review of some physical properties of ultrasound is presented, and their importance for echoencephalographic examinations is discussed.Calculations made on the basis of data concerning adult tissues, given by other authors, show that: