The aim of this study was to determine the long-term functional outcome of kidneys in children with urolithiasis treated by means of extracorporeal shock wave lithotripsy (ESWL). The effectiveness and safety of this method in the management of pediatric urinary stone disease was also studied. This prospective study enrolled 84 children, 33 boys (age: 9.1 +/- 3.8 yrs) and 51 girls (age: 9.6 +/- 3.9 yrs), with urolithiasis who were treated using a second-generation "Siemens" Lithostar lithotriptor, in the period between 1988 and 1998. Dynamic kidney scintigraphy using (99 m)Tc-DTPA was done prior to, immediately following ESWL treatment, three months later, and again after an observation period of 12 - 67 months (38 +/- 13 months). Immediate fragmentation rate was 90 %, while the calculus clearance rate was 61 %. Glomerular filtration rate (GFR), measured by clearance of (99 m)Tc-DTPA, immediately after an ESWL treatment of 107 +/- 6 ml/min was significantly lower compared to the pretreatment value of 118 +/- 7 ml/min, but returned three months later to 121 +/- 6 ml/min, and to 131 +/- 10 ml/min at the end of the observation period. A separate analysis was performed on three groups of patients treated by ESWL: with acute calculous disease, chronic calculous disease, and chronic calculous with partial stasis. ESWL treatment in children with acute obstruction was associated with an immediate increase in GFR; however, in chronic calculous disease a decrease in GFR was found. A return of GFR to the pretreatment level was observed at the three-month control in these patients. In patients with acute stone obstruction, at 3 and 12 - 67 months after ESWL treatment, GFR of the treated kidney was found to be significantly increased compared to the pretreatment level. In contrast, in children with chronic calculous disease this increase was modest. This study has demonstrated ESWL to be an effective treatment option for urinary calculi management, which can be safely performed in a pediatric population without long-term effects on the growing kidneys.