AbstractCell survival curves have been obtained for Escherichia coli B (E. coli B) after the sonication of suspensions of the bacteria with continuous wave ultrasound at a fixed frequency of 2 MHz between peak intensities of 8.7 and 2.25 W cm−2. It was found that under suitable conditions the survival curves were reproducible and it also was found that there was a clear relationship between the rate of inactivation and the peak acoustic intensity of the ultrasound. There appeared to be a lower threshold of peak intensity below which no inactivation was observed.