Purpose: Longer term comparative efficacy information regarding transobturator and retropubic mid urethral slings is needed. We report 24-month continence rates, complications and symptom outcomes from a randomized equivalence trial. Materials and Methods: Primary outcomes were objective (negative stress test, negative pad test and no re-treatment for stress urinary incontinence) and subjective (no self-report of stress urinary incontinence symptoms, no leakage episodes on 3-day bladder diary and no re-treatment for stress urinary incontinence) success at 24 months. The predetermined equivalence margin was ±12%. Results: Of 597 randomized participants 516 (86.4%) were assessed. Objective success rates for retropubic and transobturator mid urethral slings were 77.3% and 72.3%, respectively (95% CI for difference of 5.1% was -2.0, 12.1), and subjective success rates were 55.7% and 48.3%, respectively (CI for difference of 7.4% was -0.7, 15.5). Neither objective nor subjective success rates met the prespecified criteria for equivalence. Patient satisfaction (retropubic 86.3% vs transobturator 88.1%, p = 0.58), frequency of de novo urgency incontinence (retropubic 0% vs transobturator 0.3%, p = 0.99) and occurrence of mesh exposure (retropubic 4.4% vs transobturator 2.7%, p = 0.26) were not significantly different. The retropubic mid urethral sling group had higher rates of voiding dysfunction requiring surgery (3.0% vs 0%, p = 0.002) and urinary tract infections (17.1% vs 10.7%, p = 0.025), whereas the transobturator group had more neurological symptoms (9.7% vs 5.4%, p = 0.045). Conclusions: Objective success rates met the criteria for equivalence at 12 months but no longer met these criteria at 24 months. Subjective success rates remained inconclusive for equivalence. Patient satisfaction remained high and symptom severity remained markedly improved. Continued surveillance is important in women undergoing mid urethral sling surgery. © 2012 American Urological Association Education and Research, Inc.