OBJECTIVE: 1) To estimate the rate of anal incontinence and anal sphincter injury in a group of women with pelvic floor disorders; 2) to evaluate the relationship between anal incontinence and anal sphincter injury as demonstrated by endoanal ultrasonography; 3) to explore any associations between operative vaginal delivery and anal sphincter injury in this population. METHODS: A cohort of 100 women with stage II or greater pelvic organ prolapse and/or urinary incontinence completed the Rockwood-Thompson Fecal Incontinence Severity Index Questionnaire (FISI). Pelvic organ prolapse was recorded using the Pelvic Organ Prolapse Quantification system. Multichannel cystometry and endoanal ultrasonography were performed. Categorical data were compared using the chi(2) statistic. The FISI scores were correlated with degree of anal sphincter injury using the Pearson correlation coefficient (r). RESULTS: Fifteen women with pelvic organ prolapse only, 28 with urinary incontinence only, and 57 with both were evaluated. Mean age (+/- standard deviation) and body mass index were 57.1 +/- 13.2 years and 29.8 +/- 6.8 kg/m(2), respectively. Median parity was 3. Fifty-four percent of those studied had anal incontinence, and 52% had anal sphincter defects. Anal incontinence was significantly associated with sphincter injury (odds ratio 36.4, 95% confidence interval 12-114, P <.001). The FISI scores were positively correlated with increasing degrees of anal sphincter disruption (r = 0.81, P <.001). A history of operative vaginal delivery was significantly associated with anal sphincter injury (P =.023). CONCLUSION: Anal incontinence and anal sphincter injury are common in women with other pelvic floor disorders and are significantly related. Operative vaginal delivery may contribute to unrecognized anal sphincter trauma in this population. LEVEL OF EVIDENCE: III