In June 1947 a paper on the chemotherapy of leprosy based on clinical research done at the National Leprosarium was read before the Section on Dermatology and Syphilology of the American Medical Association.1In that paper the encouraging results obtained from treatment of leprosy with the sulfone drugs, glucosulfone (promin†) sodium, sulfoxone (diasone†) sodium and thiazolsulfone (promizole†), over a six year period, were presented together with a preliminary evaluation of streptomycin. After three years' additional experience, this supplemental report is made to show in what respects the present trends in treatment are in conformity with those reported three years ago and what new developments have occurred in the meantime. First of all, it should be mentioned that the use of glucosulfone, sulfoxone and a related sulfone, sulphetrone† (4,4′-bis [gamma-phenyl-N-propylaminodiphenylsulfone tetrasodium sulfonate]), has been greatly extended during the last few years and wherever these drugs have been tried encouraging results