The outgrowth of <i>Thiobacillus thioparus, T. thiooxidans, T. con <i>cretivorus, and <i>Ferrobacillus ferroxidans in culture medium was in hibited at about 35 days by 4-chloro-m-cresol vapors at 20-30°. Vapors from a composite of thymol and dicyclohexylamine in separate containers) or from 4-chloro-3,5-xylenol showed less but still significant inhibition. The use of these compounds in museum display cases is recommended to stop bacterial destruction of exhibits con -- AATA