Abstract: A lithotripter (13), and a device for the localization of calculi (11), are mounted on radially moving slides attached to the supporting ring (10). In this manner, their longitudinal axes lie in the same diametric vertical plane, and pass through the center of the supporting ring. The angular distance between the longitudinal axes of the two devices is fixed, as determined by their mounting on the ring. An echograph, with its illustrated free floating probe (19), is interfaced with a computer. The origin of the echograph coordinate system corresponds to both the center of the rotating ring, and to the calculus (16), in the patient's body (14).