The diffraction pattern of an ultrasonic wave from the top edge of a step-down was investigated experimentally, using a pulsed ultrasonic beam and a smooth, accurately formed step. The wave diffracted from the edge was separated from the reflected or scattered components by using techniques similar to those used in radar to distinguish between objects at different distances from the antenna: namely, to synchronize the horizontal sweep on an oscilloscope with the transmitted pulses so that all echoes received by the microphone appear in the scope as pips whose distance along the sweep line is a measure of the time between transmission and reception. Magnetostriction transducers were used as radiators, the signals being picked up by a Western Electric 640-AA microphone. The region from 0°–90° (from grazing angles along the top of the step to the normal) was explored and the data compared with the theoretical values derived by Sommerfeld in his paper on the diffraction at a half-plane.