Roots of seedlings of Vicia faba were exposed to 1-5 MHz continuous-wave ultrasound at approximately 5 W cm-2 intensity, averaged over the dividing region of the meristem, thus producing considerable non-thermal cell damage and severe inhibition of root growth. No significant increase in the number of coventional chromosome aberrations was observed during the 26 hours after exposure, although a significant number of cells did show bridged, agglomerated or clumped chromosomes. It is concluded that after exposure to ultrasound, genetic damage in surviving cells is unlikely.