Fluoroscopic parameters of the rectum in women with pelvic organ prolapse were studied. Ninety-eight consecutive women undergoing reconstructive pelvic surgery completed a urogynecologic history with physical examination and pelvic floor fluoroscopy. The presence of rectocele and contrast trapping was determined on each fluoroscopic study. Each frame of the study was measured to determine the rectal width. Seventy-eight per cent of the women had fluoroscopically demonstrated rectoceles. Their maximum and minimum rectal widths were larger than those of women without rectoceles. Contrast-retaining rectoceles were larger than non-contrast retaining rectoceles. Fluoroscopic evidence of contrast retention did not relate to patient symptoms. There was no difference in the grade of posterior wall prolapse in women with and without rectoceles. Rectoceles have anatomic and functional variability. Fluoroscopy may be a valuable adjunct to the physical examination in assisting gynecologic surgeons to refine their surgical approach for rectocele repair.