Objective To assess the cost effectiveness of tension-free vaginal tape compared with open Burch colposuspension as a primary treatment for urodynamic stress incontinence.

Design Cost–utility analysis alongside a multicentre randomised comparative trial.

Setting Gynaecology or Urology departments in 14 centres in the UK and Ireland, including University-associated teaching hospitals and district general hospitals.

Population Women with urodynamic stress incontinence. Exclusion criteria were: (1) detrusor overactivity; (2) major voiding problems; (3) prolapse; (4) previous surgery for incontinence or prolapse.

Methods Resource use data were collected on all 344 patients in the trial, including length of hospital stay, time in theatre and management of complications; resource use was costed using UK unit costs at 1999–2000 prices.

Main outcome measures Health outcomes were expressed in terms of quality-adjusted life years (QALYs) between baseline and six months follow up, based on women's responses to the EQ-5D health questionnaire.

Results Tension-free vaginal tape resulted in a mean cost saving of £243 (95% CI £341 to £201) compared with colposuspension. Differential mean QALYs per patient (tension-free vaginal tape − colposuspension) was 0.01 (95% CI −0.01 to 0.03). The probability of tension-free vaginal tape being, on average, less costly than colposuspension, was 100%, and the probability of tension-free vaginal tape being more cost effective than colposuspension was 94.6% if the decision-maker was willing to pay £30,000 per additional QALY.

Conclusion The results from this trial suggest that, over a post-operative period of six months, tension-free vaginal tape is a cost effective alternative to colposuspension. The results will need to be reassessed on the basis of longer follow up.