Piezoelectric scattering of conduction electrons by acoustical phonons is discussed for ZnO and CdS, and approximate values of the mobilities determined by this mechanism alone are derived. The phonon drag contribution to the Seebeck effect in ZnO is assumed to arise from crystal‐momentum exchange between electrons and acoustical phonons by way of the piezoelectric interaction alone. Comparison of the results of this assumption with the data has led to the discovery of strong piezoelectric phonon scattering from neutral donor states. These two piezoelectric scattering mechanisms and an effective electron mass of about 0.32m, derived from other experiments, provide a model for phonon drag in ZnO which agrees with the temperature dependence and ``impurity'' dependence of the data and gives the correct magnitude of the effect to within the uncertainties of the approximations employed.