The aim of this study was to compare the morbidity and short-term efficacy of retro-pubic (TVT) and inside-out trans-obturator (TVT-O) sub-urethral sling in the treatment of stress urinary incontinence. This was a prospective multi-centre randomised trial; 231 women with primary stress urinary incontinence were randomised to TVT (114) or TVT-O (117). The International Consultation on Incontinence-Short Form (ICIQ-SF), Women Irritative Prostate Symptoms Score (W-IPSS) and Patient Global Impression of Severity (PGI-S) questionnaires were used to evaluate the impact of incontinence and voiding dysfunction on QoL and to measure the patient's perception of incontinence severity. The primary and secondary outcome measures were rates of success and complications. The SPSS software was used for data analysis. The TVT-O procedure was associated with significantly shorter operation time and with a more extensive use of general anaesthesia when compared with TVT. There were 5 (4%) bladder perforations in the TVT group compared with none in the TVT-O group. Rates of early post-operative urinary retention and voiding difficulty were similar for both groups and no difference was found in the average hospital stay. Six patients (5%) in the TVT-O group complained of thigh pain in the post-operative course. The median follow-up time was 6 months. Two hundred eighteen patients were available for the analysis of outcomes. Subjective and objective cure rates were 92% and 92% in the TVT group and 87% and 89% in the TVT-O group. The ICIQ-SF questionnaire symptoms score showed a highly statistical decrease in both groups, the W-IPSS on the contrary was unchanged. Our data show that both procedures were equally effective in the short-term for the treatment of stress urinary incontinence with a highly significant improvement in incontinence-related QoL.