The morphologically recognizable effects of highly dosed ultrasound application on the growing rabbit's larynx (5 Watt/cm2 for 10 min) were studied by means of scanning electron microscopic (SEM) and reflecting light microscopic (RLM) methods. It could be shown that the area of cartilaginous necrosis corresponded exactly to the location of ultrasound application and was sharply limited by the normal cartilage. After a survival period of six weeks, areas of chondroneogenesis became visible on the endolaryngeal perichondrium. After a survival period of twelve weeks, an outer zone of cartilaginous necrosis was still to be seen. Connective tissue directly affected by ultrasound and the endolaryngeal muscles did not show any retarded damage. The results of our experiments permit to state that highly dose ultrasound application on the cartilaginous framework leads to a growth retardation with a subsequent alteration in form and shape.