Shock wave lithotripsy (SWL) is a first-line option for treatment for urinary calculi - particularly effective for the removal of uncomplicated stones from the upper urinary tract. The success of lithotripsy is tempered, however, by the occurrence of acute injury that has been reported to progress to long-term complications. SW trauma to the kidney is a vascular lesion characterized by parenchymal and subcapsular bleeding. The acute lesion is dose-dependent, and typically localized to the focal volume of the lithotripter. Cavitation has been implicated in vessel rupture, but SW-shear has the potential to be a primary mechanism for damage as well. Possible chronic adverse effects of SWL may include new-onset hypertension, development of diabetes, and exacerbation of stone disease. If acute trauma could be reduced, it seems likely that serious long-term effects could be minimized, or even eliminated. Reducing the dose of SW's needed for stone breakage is one option. Improved coupling improves stone breakage, and slowing SW rate significantly improves stone-free outcomes. Experiments with animals now show that treatment protocols can be designed to protect against tissue injury. Initiating treatment with low energy SW's dramatically reduces lesion size, and reducing the rate of SW delivery virtually eliminates SW trauma altogether. SWL stands to gain from new advances in technology, as lithotripters become safer and more effective. Perhaps the greatest progress will be made when we have determined the physical mechanisms of SW action both for stone breakage and tissue damage, and have better characterized the biological response to SW's - as this will provide the principles needed to achieve the best combination of safety and efficiency with whatever lithotripter is at hand.