Enhancement of the cavitational effect of iodine release from sodium iodide solution during repetitive 1‐MHz tone burst excitation of the solution of a rotating test tube has been reported. [V. Ciaravino, H. G. Flynn, and M. W. Miller, Ultrasound Med. Biol.7, 159–166 (1981)]. This enhancement was attributed to concurrent operation of two mechanisms: depletion of small nuclei from the cw mode size distribution generated during a tone burst, and survival from the previous tone burst of small nuclei lying in the same size range that is depleted in the cw mode. Twenty‐four hours after exposing C1300 neuroblatoma cells (N2A) in rotating tubes to 1‐MHz ultrasound tone bursts [1:1, durations from 6 to 600 ms; 3.4 W/cm2spatial peak, burst average intensity, and 5 min total treatment duration (on + off periods)] at 37°C, enhancement of protein synthesis compared to control cells was observed. Protein synthesis was measured by uptake of3H‐leucine. The similarity between results observed for cavitation‐stimulated iodine release and cellular protein synthesis is highly suggestive of cavitation as the cause for this biological effect. [Work supported by PHS.]