The aim of this study was to determine if digital assessment of anal sphincter tone predicts whether a rectal balloon is needed to prevent incontinence during a barium enema examination. During an 8 month , 306 patients scheduled for barium enema examination were evaluated. Immediately before each examination as good, fair, or poor. The barium enema was then performed in a conventional manner. Leakage of even small amounts of barium was scored as rectal incontinence. Ability to retain the barium enema correlated closely with the strength of rectal bone, regardless of patient sex or age. For different sphincter tones the incidence of rectal incontinence was: good, 2%, fair, 30%; and poor, 90%. From these findings it is recommended that, irrespective of patient age and sex, the use of rectal balloon catheters be limited to patients with poor or fair rectal tone.