Two groups of patients with altered bowel habit and pelvic floor dysfunction, but comparable epidemiologic characteristics (i.e. n = 105 each; mean age and SD 47.3 +/- 15.8 yrs vs. 54.9 +/- 16.7 yrs; range 15-80 yrs vs. 9-88 yrs; F/M ratio 28:1 vs. 2.6:1) with the exception of the absence (or presence) of fecal incontinence, were examined with defecography, taking into account criteria other than anorectal angle values and anorectal junction mobility. At the Receiver Operating Characteristic (ROC) analysis a "barium leak sign", occurring either at rest or on straining was found to be a highly reliable index of fecal incontinence (specificity: 100% and 92-93%, respectively, intraobserver agreement K value = 0.82, Z = 21.58, p 10 mm at rest; (b) poor stop test (inability to interrupt the barium stream); (c) rectal diameter > 6.5 cm and < 4 cm (abnormally increased and reduced compliance, respectively). Defecography is a useful diagnostic tool in fecal incontinence and should precede anal endosonography, manometry and electromyography for proper therapeutic decision-making and in risk conditions, e.g., in the patients about to undergo elective pelvic surgery.