(250 words) Objective To assess whether the Er:YAG laser is superior to sham in the treatment of women with mild/moderate stress urinary incontinence (SUI). Design A single blinded, multi-centre RCT comparing the Er:YAG laser to sham in women with mild/moderate SUI. Setting Three urogynaecology departments based in United Kingdom, Switzerland and Germany. Population or Sample 79 participants were recruited from urogynaecology clinics with mild/ moderate SUI. Methods Participants were randomised (2 active:1 sham) receiving 3 treatment sessions 1-2 months apart with the sham arm having energy transmission blocked. Participants were assessed at baseline and 6 months post final treatment. Main Outcome Measures Primary outcome measure: success defined as at least 50% reduction in 1hr pad weigh test (PWT) at 6 months compared to baseline (as per FDA guidelines). Secondary outcomes: Change in (ICIQ-UI SF), (PISQ-12), cough test standing and supine and visual analogue score for pain. Results 74 patients completed the study: 51 participants in laser group and 23 in the sham group. There was no difference between groups in for age, BMI, parity, smoking and diabetic status. There was a statistically significant improvement in patients treated with laser in 1hour PWT, ICIQ-UI SF and PISQ-12 at 6 months (3g, p=0.002, 5 points, p<0.001 and 6 points, p<0.001 respectively) which was not seen in the sham group. There was no change in cough test at 6 months except on standing in the sham group. Conclusions This fully powered RCT demonstrates a beneficial effect of Er:YAG laser in women with mild / moderate SUI.