ABSTRACT: A review and analysis of studies of the effects of ultrasound exposure on human fetuses leads to a conclusion that there is no association of exposure with birthweight, hearing loss, or major congenital anomalies. Conflicting data from studies on birthweight is probably due to methodologic problems with the studies that have found positive associations. There have been few sound studies of the effects of in utero ultrasound exposure in humans. Limited studies to date are mostly reassuring, but it is premature to say that ultrasound has been proven safe for the human fetus. Further research on the question of biological effects of ultrasound in humans is needed, particularly the question of a possible association of ultrasound with dyslexia.