PURPOSE: To compare prospectively and randomly tension-free vaginal tape(TVT) with transobturator vaginal tape inside-out(TVT-O) for the surgical treatment of female stress urinary incontinence(SUI). MATERIALS AND METHODS: One hundred twenty women with SUI were alternately assigned to either the TVT group(n=60) or TVT-O group(n=60). The preoperative evaluation included urodynamic study and a Korean version of the incontinence quality of life questionnaire(I-QoL). At 1-year after operation, surgical outcome, patient I-QoL parameters, long-term complications and uroflowmetry were evaluated in 2 groups. RESULTS: Preoperative patient characteristics including I-QoL and urodynamic study were comparable in the two groups. The rates of cure(86.8% for TVT vs. 86.8% for TVT-O), improvement(6.6% for TVT vs. 8.2% for TVT-O), and failure (6.6% for TVT vs. 5.0% for TVT-O) were similar for the two groups. The I-QoL parameters one year after surgery were improved significantly in both groups(p<0.001) and there was no difference between the two groups(p>0.05). The rates of the patient satisfaction with the procedure were 93.4% in the TVT group versus 95.0% in the TVT-O group(p>0.05). Mean operation time(11.5+/-1.4 min versus 15.2+/-1.8 min, p<0.05) was significantly shorter in the TVT-O than TVT. There were no long-term complications, such as vaginal erosion and prolonged voiding difficulty, in either group. CONCLUSION: TVT-O appears to be equally effective as TVT for the surgical treatment of stress urinary incontinence in women at a 1-year follow-up.