Objective: The purpose of this study was to evaluate the accuracy of magnetic resonance imaging (MRI) in the pre and postoperative assessment of stress urinary incontinence. Methods:: Fifteen female patients with clinical evidence of stress urinary incontinence were included in this prospective study. All the patients underwent MRI ill the Supine position both preoperatively and postoperatively. For imaging. we used a 1.0 T magnet. T2-weighted images were obtained in the midline sagittal plane with patients at rest. Images were evaluated for anatomical stress urinary incontinence alterations. such as the increased distance between the pubococcygeal line and the bladder base and the posterior urethro-vesical angle and the urethral inclination angle changes. Wilcoxon signed rank test allowed comparisons of pre and postoperative results. Results: Compared with postoperative measurements, the bladder base was lowered significantly by an average of 9.4+/-4.0 mm (P<0.01), posterior urethro-vesical angle was significantly increased by an average of 127.8&PLUSMN;11.4&DEG; (P<0.01). and the urethral inclination angle was significantly increased by an average of 54.9+/-10.1degrees (P<0.01) preoperatively. Conclusion: Our results suggest that MRI can play a major role in the preoperative and postoperative assessment of stress urinary incontinence. It call reliably detect anatomical urinary incontinence alterations. MRI should be considered in failed surgery, complex prolapse. and in differentiating genuine stress incontinence resulting from malposition of the bladder neck from stress incontinence due to intrinsic urethral damage. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.