OBJECTIVE Our goal was to determine the anatomic differences in pelvic floor anatomy for continent women and women with stress incontinence using MR imaging and to assess whether these anatomic differences depend on the position of the subject during imaging. METHODS Eight continent volunteers and eight women with stress incontinence underwent MR imaging in the supine and sitting positions. For imaging, we used an open-configuration 0.5-T magnet. T2-weighted images were obtained in the midline sagittal plane with subjects at rest and at maximal pelvic floor strain in 5 sec using a modified fast spin-echo sequence. In the axial plane, thin-section T2-weighted images were obtained with subjects at rest using a standard fast spin-echo technique. Images were evaluated for mobility of the urethra and bladder neck and for integrity of the vagina, levator ani, and supporting fascia. RESULTS Pelvic floor laxity and abnormalities of the supporting fascia were more common in incontinent women than in continent women. Both descent of the bladder neck when subjects strained and the posterior urethrovesical angle were not significantly greater when subjects were measured in the sitting position (p < .1). CONCLUSIONS Changes of pelvic floor laxity related to incontinence can be seen with subjects in both the supine and the sitting positions but are increased in the sitting position.