Forty-three patients whose principal symptom was pruritus ani were studied. Twenty-eight had anal disease, while in 15 no such disease could be shown. Maximum resting pressures and transient and sustained pressures of the anal canal in response to rectal distension were measured by manometry. Although the maximum resting pressure in the patients with no disease was about the same as that in the group with disease, the pressures recorded in response to rectal distension were significantly lower. These results show that the anal sphincter relaxes in response to rectal distension more readily in patients with no anal disease. Hence soiling may occur, which may be a factor in the genesis of pruritus ani.