The density, sound velocity, and ultrasonic attenuation coefficient of aqueous solutions of urea were measured at temperatures between 10 degreesC and 35 degreesC and at concentrations ranging from 0 to 9 mol/L (equivalent to21.7 mol %) urea. The data are correlated using simple empirical expressions, and the isentropic compressibilities are calculated. These urea solutions provide a favorable set of reference data for acoustical measurements of liquids with sound velocity between 1500 m(.)s(-1) and 1700 m(.)s(-1).