Abstract⎯The biophysical aspects of the effects of ultrasound on biological tissues are considered. A mathematical model that describes the effects of the primary interaction of mechanical vibrations of a resilient medium (therapeutic ultrasound in the frequency range of 800–3000 kHz) with biological tissues, was developed. The model is represented by a system of three ordinary differential equations of the first order that describe the dependence of the rate of temperature change in biological tissue exposed to ultrasound and the concentration of live cells on the intensity of ultrasonic radiation.