The anorectal function in 3 patients with bilateral and 4 patients with unilateral well-defined loss of sacral nerves after radical tumour excision was studied by clinical examination and by simultaneous registration of the following variables: volume and pressure in the rectum, pressure in the internal anal sphincter area and myoelectrical activity in the external anal sphincter. The patients with bilateral loss of sacral nerves had serious impairment of function. Constipation was their only safeguard against incontinence. The preservation of the first and second sacral nerves bilaterally was not sufficient for discrimination between different qualities of rectal contents passing the anal canal. The sensation of rectal distension was also impaired. The reflex pattern of the internal anal sphincter was, however, intact. The external anal sphincter displayed a weak spontaneous myoelectrical activity in the patients who had at least one second sacral nerve intact, and a weak increase of the activity could be induced voluntarily. The normal transient increase of myoelectrical discharge from the external anal sphincter in response to rectal distension could not, however, be elicited. In patients with total unilateral loss of the sacral nerves no significant impairment of anorectal function was noted. Total one-sided denervation implied deficient sensibility of the anal canal unilaterally, but no disturbance of sphincter function as judged from the reflex response of the internal and external anal sphincters to rectal distension.