Severe skin injury after extracorporeal shock wave lithotripsy (ESWL) is rare. We describe two patients who suffered full thickness skin burns following ESWL for renal calculi. One patient was treated conservatively and the other underwent debridement with skin grafting. We speculate that failure of the thermostatic mechanism of the lithotripter, leading to overheating of the water-filled cushion, resulted in this very rare adverse event. Proper preoperative patient counseling regarding the risk of serious burn injuries will help to avoid potential litigation.