To assess the learning curve of flexible ureteroscopic stone extraction using the UroMentor™ simulator and transfer of flexible ureteroscopic stone extraction skills to the operating theatre. MATERIALS AND METHODS: After obtaining ethics approval, urology Post-Graduate Trainees (PGTs) from Post-Graduate Years (PGYs) 1 to 4 were recruited. During phase I, participants completed 3 weekly 1-hour training sessions on the UroMentor simulator practicing task 10, where two stones from the left proximal ureter and renal pelvis were extracted using a basket. Objective assessments by the simulator and subjective assessments using the validated Ureteroscopy-Global Rating Scale (URS-GRS) were used to establish the learning curve. During phase II, the URS-GRS tool was used to assess performance of participants in the operating theatre. URS-GRS scores obtained on the simulator and in the operating theatre were correlated. RESULTS: In phase I, eight urology PGTs (PGY1-4) with mean age of 27.8 ± 2 (25-31) years participated in the study. PGTs practiced a total of 52 times, with a mean operative time of 14.6 ± 4.3 minutes and a mean fluoroscopy time of 10.4 ± 12 seconds. Competency in task 10 was achieved after seven trials on the UroMentor simulator. In phase II, 5 PGTs were assessed during 55 consecutive flexible ureteroscopic stone extraction in the operating theatre. The mean operative time was 51.4 ± 15.2 minutes and the mean fluoroscopy time was 29 ± 6 seconds. There was a significant positive correlation between URS-GRS scores obtained on the simulator and in the operating theatre (r = 0.9, p = 0.03), thus establishing predictive validity of performance on the UroMentor simulator. CONCLUSIONS: Competency in task 10 on the UroMentor simulator (flexible ureteroscopic stone extraction) was achieved after seven trials. Since there was a strong positive correlation between URS-GRS scores on the simulator and in the operating theatre, the skills obtained on the simulator could be transferred to the operating theatre.