OBJECTIVE: To estimate whether prolapse severity is a major contributor to urinary incontinence severity, as measured by validated incontinence questionnaires. METHODS: We analyzed data from two large female stress urinary incontinence (SUI) surgical cohorts: the Stress Incontinence Surgical Treatment Efficacy Trial (SISTEr) study (N=655) and the subsequent Trial of Mid-Urethral Slings (TOMUS) study (N=597). All participants completed a standardized baseline assessment including validated measures of symptom severity, quality of life, objective measures of urine loss (Urogenital Distress Inventory [UDI], Medical, Epidemiologic, and Social Aspects of Aging questionnaire, Incontinence Impact Questionnaire, and pad test), as well as the Pelvic Organ Prolapse Quantification assessment. Groups were compared using the χ test (categorical measures) or the one-way analysis of variance (continuous measures). Statistical significance was defined as P<.05. Results: The SISTEr and TOMUS samples were similar for many variables including age (52 and 53 years, respectively), nulliparity (9% and 12%), prior urinary incontinence (UI) surgery (14% and 13%), and prior hysterectomy (31% and 28%), but other differences necessitated separate analysis of the two cohorts. There was not a statistically significant difference in UDI scores according to prolapse stage in either study population. Patients with prior surgery for pelvic organ prolapse and SUI had more incontinence symptoms and were more bothered by their UI regardless of prolapse stage. Conclusion: Prolapse stage is not strongly or consistently associated with incontinence severity in women who select surgical treatment of SUI. Prior pelvic organ prolapse and UI surgery is associated with worse UI severity and bother. Clinical trial registration: ClinicalTrials.gov, www.clinicaltrials.gov, NCT00064662 and NCT00325039. © 2010 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams & Wilkins.