5 is maintained tightly pressed against the coil carrier 4 by a retaining ring or a ledge of the shockwave tube 2 the opposite open end of the shockwave tube 2 is covered by an acoustic lens 6 which is a converging lens the shockwave tube 2 and the exit apperature for the shockwaves formed by the acoustic lens 6 are covered by a sack 7 forming a volume 17 which is filled with a coupling agent 8 the sack 7 is applied against the skin of a patient as described below the shockwave generator 1 is positioned relative to a calculus in the patient such as a kidney stone or a gallstone so that the focal point of the acoustic lens 6 is coincident with the calculus the calculus can then be disintegrated by the shockwaves from the shockwave generator 1 the shockwave source 3 and the acoustic lens 6 of the shockwave generator 1 have respective central openings 9 and 10 the openings 9 and 10 being connected by a tube 11 the remainder of the volume between the shockwave tube 2 the tube 11 the shockwave source 3 and the acoustic lens 6 is filled with the same coupling agent 8 which is present in the sack 7 by means of channels 12 in the acoustic lens 6 an ultrasound head is introduced into the tube 11 from a rear of the shockwave source 3 and the head 13 partially projects into the volume 17 defined by the acoustic lens 6 and the sack 7 the ultrasound head 13 is provided with a seal 14 relative to the tube 11 so that no coupling agent 8 can escape the seal 14 and the rear portion of the ultrasound head.