['To study changes in mid-urethral function with dynamic MRI in stress urinary incontinent women undergoing either tension-free vaginal tape (TVT) or TVT-obturator sling operations.', 'Prospective clinical study.', 'University hospital.', 'Forty-two parous women with stress urinary incontinence recruited to dynamic magnetic resonance imaging before and after mid-urethral sling surgery. Control group of 16 healthy women.', 'Dynamic magnetic resonance imaging at rest, during pelvic floor muscle contraction, coughing and voiding with a bladder volume of 200-300 ml. X- and Y- coordinates were used to determine the location of the mid-urethra during these activities.', 'Changes in mid-urethral position after TVT and TVT-obturator operations during the different activities.', 'Postoperatively the women could elevate their mid-urethra by pelvic floor muscle contraction significantly higher than before the operation (p<0.05). Despite a different support angle between the TVT and the TVT-O mid-urethral slings, we could not see any differences in the movement patterns.'] Does dynamic MRI confirm support of the mid-urethra by TVT and TVT-O surgery for stress incontinence?