Antibacterial activity of 16 chloramphenicol derivatives and their induction ability for chloramphenicol resistance were examined. Three chloramphenicol derivatives ; CM 16 (DL-α-dichloroacetamido-β-bromo-p-nitropropiophenone), CM 17 (DL-α-dichloroacetamido-α-methylene-p-nitropropiophenone) and CM 18 (DL-α-acetamido-α-methylene-p-nitro-propiophenone) were found to be highly active against S-1477 but their inducible activity for chloramphenicol resistance was rather low. CM 26 (chloramphenicol monophosphate) and CM 29 (D-threo-2, 2-diethyl-5-dichloroacetamido-6-(p-nitrophenyl)-1, 3-dioxane) has no antibacterial activity and CM 15 (DL-threo-2-dichloromethyl-4-p-nitrophenyl-hydroxymethyl-Δ²-oxazoline) has very low activity against S-1477, but they have low inducible activity for chloramphenicol resistance in spite of no activity of other derivatives.