Introduction and hypothesis The purpose of this study is to describe risk factors for post-operative urinary tract infection (UTI) the first year after stress urinary incontinence surgery. Methods Multivariable logistic regression analyses were performed on data from 1,252 women randomized in two surgical trials, Stress Incontinence Surgical Treatment Efficacy trial (SISTEr) and Trial OfMid-Urethral Slings (TOMUS). Results Baseline recurrent UTI (rUTI; =3 in 12 months) increased the risk of UTI in the first 6 weeks in both study populations, as did sling procedure and self-catheterization in SISTEr, and bladder perforation in TOMUS. Baseline rUTI, UTI in the first 6 weeks, and PVR>100 cc at 12 months were independent risk factors for UTI between 6 weeks and 12 months in the SISTEr population. Few (2.3-2.4%) had post-operative rUTI, precluding multivariable analysis. In women with pre-operative rUTI, successful surgery (negative cough stress test) at 1 year did not appear to decrease the risk of persistent rUTI. Conclusions Pre-operative rUTI is the strongest risk factor for post-operative UTI. © 2011 The International Urogynecological Association.