Objectives. To establish virtual ureteroscopy (VU) through computed tomography urography (CTU) data from patients with upper urinary tract (UUT) stones indicated for flexible ureteroscopy (fURS) and to validate its effectiveness. Methods. Patient-specific VU generation was accomplished through incorporating CTU data into specialized software (Crusher) developed on the open access Visualization Tools Kit (VTK). These were then presented to fURS experts and novice urologists for evaluation and comparison using modified Likert-type questionnaire of 10-point rating scales (1 = not at all useful/not at all realistic/poor, 10 = very useful/very realistic/excellent). Results. Face and content validation of VU from 5 fURS experts in 3 different centers: overall usefulness 7.4 +/- 0.5, graphics 7.4 +/- 0.5, intrarenal anatomy 8.4 +/- 0.5, stone details 7.8 +/- 0.4, usefulness in surgical planning and training 7.6 +/- 0.9. Significant increase of detection in the number of calyces and stones was found from using CTU only to CTU-VU combined in the novice group (P=.000). Before VU observation, novices found much fewer calyces and stones than experts (P=.004 and .000, respectively). However, this gap disappeared after VU observation (P=.327 and .292, respectively). VU feedback from the novices was superb. Conclusions. Establishing patient-specific VU through CTU data from renal stone patients is feasible. The present VU can significantly improve novice urologists' comprehension of intrarenal anatomy and stone information before fURS procedures. Face and content validity is also proved. This novel modality may serve as an important tool for fURS surgical planning, navigation, and training.