Results are presented for the temperature and frequency dependence of the attenuation of two piezoelectrically active ultrasonic waves in ZnO: (1) compressional waves propagated along thecaxis, and (2) shear waves propagated normal to thecaxis and polarized along thecaxis. Measurements of the phonon phonon attenuation were made over the frequency range 60 MHz to 3.97 GHz and the temperature range 4.2° to 300°K. The frequency dependence at 40°K is of the 1.0 and 0.7 power for the shear and compressional modes, respectively; at 300°K. the frequency dependence is ∼1.6 for both modes. The temperature dependence ranges from at leastT4at low temperatures to essentiallyT0; at 300°K for the shear mode; the temperature dependence for compressional waves at frequencies below 2.0 GHz does not appear to reach aT4dependence for temperatures down to ∼20°K.