This volume summarizes the written report of the Watchdog Group (Safety Committee of the European Federation of National Ultrasound Societies: EFSUMB) since 1979. It gives critical comments on various publications of the ultrasound bioeffect research from the viewpoint of risk arising from the use of sonography in diagnostic medicine. The publications cover a wide range of topics, from technical problems to genetic and teratologic questions to the epidemiology of abnormalities and leukemia in children who have received intrauterine sonography. The book brings together the whole spectrum of bioeffect research in ultrasonography and will help lead to a factual discussion of ultrasound in medicine.