To evaluate the use of transperineal ultrasonography while diagnosing stress urinary incontinence (SUI) by comparing the urethral angle (α), posterior urethrovesical angle (β), and bladder neck descent (BND) during rest and Valsalva maneuver in continent women and women with SUI. This prospective observational study was conducted with 50 women with SUI and 50 continent women. Transperineal ultrasonography was performed at rest and during Valsalva maneuver. Q-tip test was performed. During the Valsalva maneuver, both α and β angles were significantly higher in women with SUI (p < 0.001). The difference between Valsalva and rest measurements of α and β angles (R α, R β) were also significantly higher in women with SUI (p < 0.001). The cut-off point determined for the R α in the diagnosis of stress incontinence was 16° (80% sensitivity, 98% specificity). A statistically significant strong correlation was found between Q-tip test angle and R α value (p=0.000; r=0.890). Q-tip VAS pain scores were significantly higher than ultrasonography VAS pain scores (p < 0.001). In relation to the bladder neck descent comparison between the two groups showed that BND was significantly higher in SUI group (p < 0.001). The cut-off point determined for BND in the diagnosis of SUI was >11mm (90% sensitivity, 98% specificity). Transperineal ultrasonography is a practical, reliable, non-invasive and comfortable method for evaluation of SUI. It has the advantage of dynamic evaluation during the Valsalva maneuver. Rotation angles and BND have high sensitivity and specificity for detection of SUI. The change in α angle with Valsalva (Rα) can be used as an alternative to Q-tip test. Copyright® by the International Brazilian Journal of Urology.