After recent reports of the successful use of extracorporeal shock-wave lithotripsy for the treatment of gallstone disease, at least 10 different manufacturers have developed lithotripsy systems and initiated clinical trials in the United States. The three major types of lithotripters, classified by the method used to generate shock waves, are the spark-gap, piezoelectric, and electromagnetic systems. Although each type of system generates shock waves by different methods, all currently available systems appear to be able to fragment gallstones. However, there does not appear to be any system that has demonstrated clear clinical superiority in terms of either efficacy or safety. Additional information, both clinical and experimental, is needed before it can be determined if the type of shockwave generator has a significant effect on outcome. Clearly more than the physical principles of shockwave lithotripters must be evaluated.