Six strains of chloramphenicol (CM)-resistant endospore-forming bacteria, which can grow in the presence of 100 microgram/ml of CM, were isolated and identified as Bacillus badius. Mechanism of CM-resistance in one of the isolated strains, Bacillus badius 211, was investigated. No inactivation of CM was demonstrated when the strain was grown in nutrient broth containing 100 microgram/ml of CM, as evidenced by paper-disc bioassay of CM in the growth medium. In accordance with this result, no CM acetylation activity was demonstrated either with the intact cells or with the crude extracts of the CM-resistant strain. Poly U- and Poly A-directed polyphenylalanine and polylysine syntheses by S--30 preparations of both CM-resistant and CM-sensitive strains of Bacillus badius were almost equally inhibited by CM. From these results, the mechanism of CM resistance in Bacillus badius 211 seems to be due to other unknown mechanism.