Clinical anal examination, manometry (resting and squeeze pressures), and single-fiber electromyography were compared with endosonography of the anal sphincters in 14 patients with fecal incontinence. Technical aspects of the procedure and normal imaging of the puborectal muscle and both sphincters were defined. Defects in both sphincters were seen in nine patients. The defect is visualized as a clear discontinuity in the muscular ring. Compared with the conventional studies, anal endosonography gave significant information in six patients (four male patients after perianal surgery and two women), showing sphincter defects in five patients and integrity of the sphincters in another one. This information obtained by endosonography was important in understanding the type and extension of the lesion and deciding upon the surgical repair. Anal endosonography is an imaging technique of the sphincters that can assess their integrity in fecal incontinence.