No data on therapeutic results obtained with infraroentgen rays (grenz rays or bucky rays) in the treatment of leishmaniasis cutis are as yet available. In a preliminary publication1 3 cases were reported by us and it was demonstrated that therapeutic effects were, indeed, achieved with this method of treatment; so it seemed worth while to study the question as to what dosage yielded optimal results. The procedure adopted for these studies was to treat several lesions in the same patient separately with varying doses. For this purpose we chose 2 patients, one with thirty lesions on his extremities and the other with seventy. In each of the 2 eight lesions of more or less equal size were treated with different doses and different qualities of rays. For a single sitting the doses varied between 500 and 2,000 r with a half value layer of 0.020 to 0.033 mm. of