Objective: To analyze the factors which affect the durability of the flexible ureteroscope and the causes of scope damage in a single academic center. Material and Method: Between March 2014 and August 2017, 479 flexible ureteroscopic procedures, using 6 flexible ureteroscopes (Olympus model URF-V), were systematically reviewed. Data including indication for procedures, auxiliary device usage, the characteristics of scope damage, and the number of times a scope was used before requiring major repair were gathered. Fisher exact test and Chi-square test were used to evaluate the factors which caused the damage. Results: The major flexible ureteroscopic procedure performed was treatment of renal calculi (81%). The most common auxiliary device used was the Holmium laser (70%). The most common cause of damage requiring repair was working channel leakage (93%). The factor that affected the durability of flexible ureteroscopes was the size of laser fiber. Utilizing laser fiber 200 nm decreased scope damage significantly compared to various other sizes (p-value=0.002 and p-value<0.001). However, the usage of nitinol basket and ureteral access sheath did not affect the durability of flexible ureteroscopes. Conclusion: Large laser fibers are a risk factor for flexible ureteroscope damage. Utilizing small laser fibers during flexible ureteroscopy can decrease scope damage significantly.