Pulses of ultrasound of finite amplitude are generated in liquids by an electrical system of 2.5‐Mc frequency and an air‐backed x‐cut quartz crystal of the same fundamental frequency. After passage through the liquid, the signals are received on a 2‐in.diameterx‐cut quartz crystal with a fundamental frequency of 25 Mc. The distortion is measured either by a Fourier analysis of the received waveform or by measurement of the various harmonics by a tunable amplifier. Photographs of the waveform at different distances from the transducer illustrate the formation of the sawtooth wave. Comparison is made between the measured harmonic content and that computed theoretically. [The work was supported in part by the Office of Naval Research and by a National Research Council Fellowship to one of the authors (A.G.L.).]