The clinical, anorectal manometric and electrophysiological findings in 24 patients with faecal incontinence, 10 of whom also had rectal prolapse, and in 8 patients with rectal prolapse without incontinence, are reported. Single fibre electromyographic studies and anal reflex latencies were abnormal, indicating damage to the innervation of the pelvic floor musculature, in all the patients with faecal incontinence, with or without rectal prolapse. These studies were normal in 7 of the 8 patients in whom rectal prolapse occurred without incontinence. These investigations imply that denervation of the sphincter musculature can be recognized by electrophysiological tests in most patients with primary faecal incontinence and that the pathogenesis of rectal prolapse differed in the two groups of patients.