The use of light diffraction for the measurement of the sound‐pressure amplitude and the waveform of ultrasonic waves has been extended to the case of ultrasonic pulses. The method has been applied to transducer calibration in water at 5 Mc for pulses of 3 to 12 μsec duration, and compared with calibration by means of continuous waves. The distortion of the waveform in ultrasonic pulses of finite amplitude is demonstrated by measurements of the transducer voltage vs light intensity in the first diffraction orders. All measurements made with continuous waves and with pulses give approximately identical results.