PURPOSE: We evaluated the influence of preoperative urodynamic studies on diagnoses, global treatment plans and outcomes in women treated with surgery for uncomplicated stress predominant urinary incontinence. MATERIALS AND METHODS: We performed a secondary analysis from a multicenter, randomized trial of the value of preoperative urodynamic studies. Physicians provided diagnoses before and after urodynamic studies and global treatment plans, defined as proceeding with surgery, surgery type, surgical modification and nonoperative therapy. Treatment plan changes and surgical outcomes between office evaluation and office evaluation plus urodynamic studies were compared by the McNemar test. RESULTS: Of 315 subjects randomized to urodynamic studies after office evaluation 294 had evaluable data. Urodynamic studies changed the office evaluation diagnoses in 167 women (56.8%), decreasing the diagnoses of overactive bladder-wet (41.6% to 25.2%, p <0.001), overactive bladder-dry (31.4% to 20.8%, p = 0.002) and intrinsic sphincter deficiency (19.4% to 12.6%, p = 0.003) but increasing the diagnosis of voiding dysfunction (2.2% to 11.9%, p <0.001). After urodynamic studies physicians canceled surgery in 4 of 294 women (1.4%), changed the incontinence procedure in 13 (4.4%) and planned to modify mid urethral sling tension (more or less obstructive) in 20 women (6.8%). Nonoperative treatment plans changed in 40 of 294 women (14%). Urodynamic study driven treatment plan changes were not associated with treatment success (OR 0.96, 95% CI 0.41, 2.25, p = 0.92) but they were associated with increased postoperative treatment for urge urinary incontinence (OR 3.23, 95% CI 1.46, 7.14, p = 0.004). CONCLUSIONS: Urodynamic studies significantly changed clinical diagnoses but infrequently changed the global treatment plan or influenced surgeon decision to cancel, change or modify surgical plans. Global treatment plan changes were associated with increased treatment for postoperative urgency urinary incontinence.