OBJECTIVE: To assess the difference in measured urethral function before and after tension-free vaginal tape procedure (TVT). METHODS: Women who underwent TVT for genuine stress incontinence with or without intrinsic sphincter deficiency completed this study. Multichannel urodynamic testing was performed preoperatively and 6 weeks postoperatively. Maximum urethral closure pressure and pressure transmission ratio were recorded. Valsalva leak point pressures were determined at 150 mL and at full bladder capacity. Resting and straining urethral angles were measured using the cotton swab technique. Subjects completed both the Incontinence Impact Questionnaire and Urodynamic Distress Inventory preoperatively and postoperatively. RESULTS: Thirty-five consecutive women were studied. Twenty-three (65.7%) had a preoperative diagnosis of intrinsic sphincter deficiency as defined by maximum urethral closure pressure less than 20 cm H2O and/or Valsalva leak point pressure less than 60 cm H2O. Subjective and objective success rates were 91% and 83%, respectively. Subjects showed an 86.8% (95% CI 71.9%, 100.0%) improvement in their Incontinence Impact Questionnaire score and a 72.9% (95% CI 62.6%, 83.1%) improvement in their Urodynamic Distress Inventory score. The mean change in maximum urethral closure pressure was −1.3 cm H2O (95% CI −5.9, 3.3), whereas the pressure transmission ratio increased 15.7% (95% CI 5.0%, 26.3%). The mean decrease in straining urethral angle was 16.3° (95% CI −23.9°, −8.7°). Cured subjects demonstrating hypermobility preoperatively continued to do so postoperatively. CONCLUSION: There was a significant increase in pressure transmission ratio, but not maximum urethral closure pressure, after TVT. These changes are similar to those reported after retropubic urethropexy and traditional sling procedures. The effectiveness of the TVT sling does not appear to depend on a clinically significant change in the straining urethral angle.