Probe microphones are now in such common use and obtainable in so many different forms that it seems appropriate that a description of the various forms and a comparison of their salient features be set down. This paper discusses (1) the simple probe microphone, which consists of a tube terminating in the diaphragm of a pressure‐sensitive transducer; (2) the terminated probe microphone, which consists of a tube terminated in the diaphragm of a pressure‐sensitive transducer in parallel with which has been placed the characteristic impedance of the probe tube; and (3) the resistively tipped microphone, in which the damping resistor is placed at the tip of the probe and the probe tube is terminated in a pressure‐sensitive diaphragm. In addition to comments on the three types of probes, a suggestion for a figure of merit for probe‐tube microphones is also set down. Much of the work done on probe microphones is not original with this author, and proper credit is made to all sources known to the author.