Anorectal function was prospectively evaluated in 43 consecutive patients with fecal incontinence and in 19 healthy volunteers using manometry and electrical stimulation of the anoderm. Both anorectal motor and sensory function was impaired in incontinent patients as compared with healthy controls. Further statistical analysis identified four subgroups of patients showing different pathomechanisms of fecal incontinence: severe combined anorectal motor and sensory dysfunction, isolated anal sphincter dysfunction, isolated anorectal sensory dysfunction, and combined dysfunction of the internal anal sphincter and impaired anorectal sensitivity. These data support the hypothesis that sensory function of both the rectum and the anal canal is an important and independent factor in the preservation of continence.