The results of skin and nasal scrapings are recorded in 146 cases of leprosy during periods of sulfone thaerapy ranging from six to ten years 1- The nasal mucosa is apparently freed of M. leprae in more than 50 per cent of cases within one year of sulfonetreatment. 2- The skin is apparently freed of M. leprae, as shown by routine skin scrapings, in less than 10 per cent of cases in from one to ten years of sulfonetreatment.