To estimate whether a strategy of immediate surgery was noninferior to a strategy based on discordant urodynamic findings followed by individually tailored therapy in women with stress urinary incontinence (SUI).A multicenter diagnostic cohort study with an embedded noninferiority randomized controlled trial was conducted in six academic and 24 nonacademic Dutch hospitals. Women with predominant SUI eligible for surgical treatment based on clinical assessment were included between January 2009 and November 2010. All patients underwent urodynamics. In patients in whom urodynamics were discordant with clinical assessment, participants were randomly allocated to receive either immediate surgery or individually tailored therapy based on urodynamics. The primary outcome was clinical improvement assessed by the Urogenital Distress Inventory 12 months after baseline. Analysis was by intention to treat; a difference in mean improvement of 5 points or less was considered noninferior.Five hundred seventy-eight women with SUI were studied, of whom 268 (46%) had discordant findings. One hundred twenty-six patients gave informed consent for randomization and were allocated to receive immediate surgery (n=64) or individually tailored therapy (n=62). The mean improvement measured with the Urogenital Distress Inventory after 1 year was 44 points (?24) in the group receiving immediate surgery and 39 (?25) points in the group receiving individually tailored treatment. The difference in mean improvement was 5 points in favor of the group receiving immediate surgery (95% confidence interval -? to 5). There were no differences with respect to cure or complication rate.In women with uncomplicated SUI, an immediate midurethral sling operation is not inferior to individually tailored treatment based on urodynamic findings.ClinicalTrials.gov, www.clinicaltrials.gov, NCT00814749.I.