Extracorporeal shock wave lithotripsy was performed for treatment of calculi of the upper urinary tract in 73 children. All patients were treated with the standard HM3 Dornier lithotriptor. A total of 138 calculi in 86 renal units was treated, requiring 111 extracorporeal shock wave lithotripsy sessions. After therapy no serious complications were encountered. Six months after treatment 79 per cent of the patients were free of stones and 17 per cent had small residual fragments (less than 3 mm.), while extracorporeal shock wave lithotripsy was considered to be unsuccessful in 3 children, although disintegration could be obtained in all patients. During a median followup of 24 months (range 13 to 40 months) growth of residual fragments was noted in 33 per cent of the patients and the recurrence rate was 10 per cent.