Knowledge of the mechanism of tissue damage by ultrasound of low megahertz range is essential for prediction of safe dosage levels for diagnostic applications as well as for the prediction of the reproducibility of its therapeutic effects. This communication will deal with the cavitational aspects of tissue damage. Studies on ultrasonic irradiation of prepared non-biological liquids showed characteristic acoustic emissions of strong half-harmonic signals from the media, the power content of which was found to be fairly stable. The half-harmonic power has been defined as the “cavitation intensity,” which was found to increase exponentially with the irradiation intensity. Similar studies on blood plasma and frog liver confirmed the presence of cavitation as well as the functional relationship between the cavitation intensity and the irradiation intensity. The acoustic emission from the target during the ultrasonic irradiation of the cat brain was also characteristic of cavitation. For focused beams of ultrasound, as are normally used to cause focal lesions at the target, the cavitation intensity distribution at the target was computed from the acoustic intensity distribution. In order to predict the ultrasonic damage to structurally homogenous tissues, the computed cavitation intensity was correlated with the stress and energy intensity in the media. Based on the nature of the cavitation spectrum, statistical models were developed to predict tissue damage, due to single ultrasonic bursts, as a function of irradiation parameters, viz., the total acoustic power, pulse duration, and irradiation frequency. The predicted damage has been found to correlate well with the published experimental data.