The corner‐reflector antenna for electromagnetic radiation has been studied theoretically by J. B. Kraus [Proc. Inst. Radio Engrs.28, 513 (1940)] and experimentally by E. F. Harris [Proc. Inst. Radio Engrs.41, 645 (1953)], as well as others. However, little use has been made of analogous reflector for beam pattern formation with sonar transducers. The simple image theory of the corner reflector is reviewed in the light of applications to the acoustic case. Theoretical results for reflected impedance, forward gain, and radiation pattern are in good agreement with experimental results. In order to obtain a narrow‐beam, high intensity underwater‐sound projector, a corner reflector has been constructed, tested, and used. The transducer element consists of a line of BaT:O cylinders located in the bisectional plane of a 90° corner reflector. Impedance, gain and pattern have been investigated as a function of the distance in wavelengths of the transducer element from the line of intersection of the two reflecting surfaces. To date, only the 90° reflector has been examined. As a means for acoustic‐pattern formation, the corner reflector is of simpler construction than the cylindrical parabola and offers the advantage that the beam pattern can be readily changed by altering the reflector position and angle.