In a recent review of acoustic studies (essentially absorption of longitudinal and shear ultrasonic waves) of polymer solutions, Peth-rick [l] dealt mainly with polymers in organic solvents. For such systems the methods based on ultrasonic absorption are very useful for providing kinetic information on “processes involving segmental motion of the backbone, side groups and overall cooperative motion of the whole molecule”. The scope of the present paper is to review the ultrasonic studies of polyelectrolytes and biopoly-electrolytes in aqueous solutions. In addition to ultrasonic absorption, studies related to ultrasonic vibration potential and to ultrasonic velocity of polyelectrolyte solutions are also reviewed. A great wealth of information, both thermodynamic and kinetic, has been gained by such studies of polyelectrolyte solutions. It is hoped that this review will help stimulate further research in this field.