AS A RESULT of preliminary trials with diiodohydroxyquinoline (diodoquin®) as a topical therapeutic agent,1we reported that (1) satisfactory antibacterial and antifungal effects were obtained, (2) irritation and sensitization failed to occur even in dermatoses that are frequently intolerant and (3) the staining effect of the drug was comparatively trivial. Diiodohydroxyquinoline (5,7-diiodo-8-hydroxyquinoline) is a fine pale yellow powder containing 63.9 per cent of iodine which is used orally in the treatment of amebiasis and other protozoal intestinal infections and vaginally (in the preparation floraquin®) in the treatment of trichomonas infection. Diiodohydroxyquinoline is insoluble in water, dilute acids and alkalis and is readily incorporated into ointments. Chemically it is closely related to certain other commonly used quinoline derivatives2: quinolor,® a mixture of 5-chlor-8-hydroxyquinoline, 7-chlor-8-hydroxyquinoline and 5,7-dichlor-8-hydroxyquinoline; iodochlorohydroxyquinoline (vioform®), 5-chloro-7-iodo-8-hydroxyquinoline; sterosan, 5,7-dichlor-8-hydroxyquinaldine, and surfen, a German proprietary quinoline derivative.