Objective: Extracorporeal shock wave lithotripsy (ESWL) is a successful treatment approach for upper urinary tract calculi. However, presence of calculi resistant to shock wave may result in an increase in treatment costs, prolonged treatment period and undue exposure of renal parenchyma to shock waves. In this study, we investigated the efficacy of conventional X-ray imaging radiodensity in detecting ESWL resistant renal calculi before treatment. Material and Methods: One hundred sixty two patients who underwent ESWL for treatment of urinary tract calculi between September 2002 and March 2004 were retrospectively included in this study. Direct urinary tract radiographs of patients were scanned with resolution of 200 dpi and gray scale levels of the stones were determined using a graphic program. Patients were divided in two groups as having renal (90) and urethral calculi (72) and fragility of the calculus by shock waves were compared according to their gray scale levels. Results: When renal calculi were evaluated as fragmentation positive and negative groups, fragmentation by ESWL was observed in 76 of 90 renal stones (84.5%). While the gray scale level of calculi in the direct radiographs of fragmentation positive renal calculi group was determined as 125 +/- 49, this level was determined as 132 +/- 50 in fragmentation negative group (p= 0.6731). With respect to ureteral calculi, fragmentation was observed in 51 patients (70%). The average gray scale levels of ureteral calculi in fragmentation positive and negative groups were measured as 11 +/- 53 and 108 +/- 37 respectively. No significant difference was found between these levels (p= 0.6198). Conclusion: These results demonstrate that gray scale level of urinary calculi failed to be effective to determine the possibility of fragmentation of urinary calculi before ESWL treatment.