Since sulfone drugs were introduced in the treatment of leprosy the evolution of this disease has been considerably modified, but, unfortunately, the episodes of lepra reaction which occur in the course of the lepromatous form are not influenced by sulfone therapy. The lepra-reaction syndrome is characterized by erythema nodosum, neuritis, joint and muscle pains, and constitutional symptoms. Recent published reports indicate a favorable influence of corticotropin (ACTH) and cortisone on the lepra reaction. Johansen and Erickson,1 in a review of the treatment of leprosy, stated that cortisone seemed to be of value in the treatment of this reaction and leprous iridocyclitis, and Roche and his associates2 also believe that corticotropin controls the lepra reaction and should prove a useful adjunct in the treatment of leprosy. The following cases are reported to show the results of the use of corticotropin on the lepra reaction. The six cases