Objective: Sphincter defects are a common cause of fecal incontinence (FI). We examined FI severity and medical factors to determine their association with sphincter defects on anal ultrasound ( US ). Methods: We examined data from a cohort of patients with FI who had US performed in our institution from 2001 to 2005. Data were obtained from self-report questionnaires, anorectal physiology testing, and US. Univariate (Chi square and t-tests) and multivariate (logistic regression) analyses were performed to determine which factors were associated with sphincter defects. Results: Of 613 patients with FI, 491 (57 men) had US performed. We divided our cohort into two groups; 59% had intact sphincters and 41% had a defect in the external, internal, or both sphincters. The mean age was 61±14 years in those with no defect and 52±14 years in those with a defect (p<.001). Women were more likely to have a sphincter defect than men (43% vs. 23%, p<.003). Sphincter defects were also associated with less constipation (11% vs. 23%, p=.001) and higher prevalence of anal surgery (37% vs. 21% p<.001). No significant differences between groups were noted for loss of mucus, liquid, or solid stool, urine leakage, sense of urgency, pad use, and incomplete evacuation. Among patients with defects, men reported more anal surgery than women (85% vs. 34%, p<.001). Those with no defects were more likely to be diabetic (p=.016) and have a unilateral pudendal neuropathy (left nerve: p=.013; right nerve: p=.038). In women, episiotomy, forceps or vacuum delivery, prolonged labor, and tear at delivery were related to presence of a defect (p's <.001-.02). Multivariate analysis showed that younger age (p<.001), being female (p<.004), anal surgery (p<.001), less constipation (p<.001), and tear at delivery (p<.001), and were independently associated with a sphincter defect. Conclusions: Our data show patients with a sphincter defect are more likely to be younger, women with a tear at the time of delivery, or men with a history of anal surgery. Patients with no sphincter defects are likely to have other causes of FI, such as diabetes or pudendal neuropathy. Interestingly, the presence of a sphincter defect did not predict FI severity. Despite the different etiologies for FI in these two groups, their clinical characteristics are quite similar, indicating that complete evaluation including US should be performed in all patients regardless of FI severity or associated symptoms.