Conventional assessment of anorectal function with defecating videoproctography is semiquantitative and the high radiation exposure precludes prolonged or repeated testing. The aim of this study was to develop a dynamic scintigraphic method of assessing anorectal function.Fourteen patients with fecal incontinence, 18 patients with chronic constipation, and 8 control subjects were assessed by scintigraphic defecography. This involves introduction of a technetium-99m-radiolabeled artificial stool into the rectum of the subject and acquisition of gamma camera images during evacuation.Mean evacuation rate was 2.8 percent/second in incontinent patients and 0.9 percent/second in constipated patients (P < 0.001). The mean anorectal angles were 136 degrees and 133 degrees, respectively. There were 18 cases of pelvic floor descent and 6 rectoceles. Scintigraphic defecography provides quantitative information on rectal evacuation. Anorectal angle and pelvic floor movement can be examined. The radiation dose to pelvic organs is significantly less than with videoproctography.We believe that scintigraphic defecography is the investigation of choice for objective and dynamic assessment of anorectal function.