An instrument called the Borehole Televiewer has been developed for making acoustic pictures of the walls of a borehole. Very often certain problems in exploration and production of oil can be solved from information gained by looking at the face of the borehole. Owing to the fact that the well is usually filled with an opaque liquid such as drilling mud or oil, optical devices (e.g., cameras or television) cannot be used. The Televiewer, using pulsed 2‐mHz sound, scans the borehole wall. From the amplitude of the reflected signal a pictorial representation of the wall is made. The form of the picture is as if the well were vertically split in the magnetic north direction, unfolded and laid flat. Well features are reproduced in extraordinary detail on the resulting pictures. Azimuthal resolution is on the order of132 in., which is unusual when one considers that the piezoelectric transducer is a disk12 in.in diameter.