The performance of freeze concentration at constant freezing rate (40 mm h(-1)) with/without ultrasonic irradiation was examined using three one-component solutions containing only one solute (ionic or molecular concentration: 0.03 mol L-1) and a three-component solution containing three solutes (each component concentration: 0.01 mol L-1). Without ultrasonic irradiation the solutes are hardly concentrated at this freezing rate. On the other hand, with ultrasonic irradiation, the concentration efficiency increases with increasing intensity of ultrasonic irradiation. The solutes of smaller molecular weight are concentrated more effectively than solutes of larger molecular weight, regardless of the intensity of ultrasonic irradiation. This corresponds well to the magnitude of the diffusion coefficient of each solute. The difference between the concentration efficiencies of each solute in the three-component solution is smaller than that between the concentration efficiencies in the one-component solution, but the order of the values of the efficiencies is the same.