Purpose: To retrospectively evaluate the effect of a log-rolling procedure and postvoiding residual (PVR) bladder urine volume on opacification of urinary bladder and ureters at multi-detector row computed tomographic (CT) urography. Materials and Methods: Institutional review board approval was obtained, and informed consent was waived for this retrospective HIPAAcompliant study. Triple-phase 16- or 64-detector row CT urographic images in 166 patients (88 men, 78 women; mean age, 58.9 years; range, 22-89 years) were evaluated retrospectively. Immediately prior to excretory phase scanning, 67 patients did and 99 did not undergo a log-rolling procedure on the CT table. PVR bladder urine volume was quantified as the largest cross-sectional area of the bladder measured on unenhanced images (PVR values). The degree of bladder opacification was quantified as the percentage of the total cross-sectional area of the bladder that was opacified on excretory phase images. Ureteral opacification was quantified as the percentage of ureteral length that contained enhanced urine. On the basis of PVR values, patients were stratified into four subgroups (≤2000, >2000 to ≤3000, >3000 to ≤4000, and >4000 mm 2). The Wilcoxon rank sum and Student t tests were used to evaluate differences. Results: Median degree of bladder opacification of the log-rolling versus non-log-rolling group was 100% versus 78% for PVR values of 2000 mm 2 or less (P < .01), 99% versus 79% for PVR values of more than 2000 to 3000 mm2 or less (P = .01), 89% versus 79% for PVR values of more than 3000 to 4000 mm2 or less (P < .05), and 64% versus 69% for PVR values of more than 4000 mm2 (P = .96). There was no significant difference between ureteral opacification and log rolling or between bladder and ureteral opacification (P > .05). Conclusion: Use of a log-rolling procedure prior to excretory phase CT urography increases the percentage of bladder opacification in patients with PVR values of 4000 mm 2 or less. No difference in ureteral opacification was observed between the log-rolling and non-log-rolling groups.