A model to simulate cooling crystallization processes with ultrasound is proposed by introducing an additional kinetic expression for nucleation mechanism due to the ultrasound irradiation. Applying the model to predict the concentration profiles, nucleation rates, and crystal-size distribution during the sonocrystallization process shows that the key parameter for understanding induced nucleation seems to be the reduction of the nucleation work, which verifies the assumption of a heterogeneous-nucleation mechanism. Hence, the specific foreign surfaces of the cavitation bubbles as well as the adsorption properties of the forming crystals on the cavitation bubbles play important roles in qualitative prediction of the number of induced nuclei. Furthermore, enhanced diffusion due to ultrasonic waves seems to have a minor effect on the nucleation mechanism. (C) 2009 Elsevier Ltd. All rights reserved.