The non-invasive disintegration of kidney stones using shock waves, referred to as extracorporal shock wave lithotripsy, has been successful for more than twenty years in treating patients having renal and ureteral stones. Two modified shock wave generators are described in this article. The novel systems produce two similar shock waves (tandem shock waves) generated with a short time delay. The second shock wave arrives during collapse of the bubbles generated in the neighborhood of the stone due to the first shock wave. This may increase cavitation bubble collapse and could enhance cavitation-induced damage to kidney stones during shock wave lithotripsy. In vitro comparison of standard systems with the new designs showed that fragmentation efficiency of artificial kidney stones was significantly enhanced using tandem shock waves.