Ultrasonic spectroscopy provided a powerful, efficient, and reliable tool for a number of investigations, including those of polymer solution dynamics, molecular interaction, and the miscibility and compatibility of biopolymers in aqueous solutions. Ultrasonic velocity and related acoustic parameters were measured as a function of the concentration of poly(vinyl alcohol) (PVA), dextran, and a PVA-dextran mixture in water with the resonance method at a frequency of 3 MHz over a temperature range of 20-50degreesC. From the comparative results of sound velocity, density, adiabatic compressibility, acoustic impedance, and viscosity relaxation time as a function of temperature and concentration, the mode of interaction and the compatibility and miscibility between the two biologically active macromolecules were probed and were considerable at all concentrations and temperatures because of crosslinking via hydrogen bonding involving the hydroxyl groups of both of the biomacromolecules. The interpretations of the acoustic results were confirmed by the intrinsic viscosities of the ternary systems. The significant interaction and compatibility of these biopolymers should lead to the development of pharmaceutically active molecules. (C) 2003 Wiley Periodicals, Inc.