Chloramphenicol-3-acetate esterase activity was detected in cell-free extracts of strains of Streptomyces venezuela, Streptomyces sp. and Streptosporangium viridogriseum var. kofuense which produced chloramphenicol and also Corynebacterium hydrocarboclastus which produced chloramphenicol analogs (corynecins). None of the cell-free extracts of chloramphenicol- or corynecin-producing strains possessed chloramphenicol acetyltransferase activity under conditions which avoided the influenced of the esterase activity. Among 20 strains examined that did not produce chloramphenicol, chloramphenicol acetyltransferase was detected in cell-free extracts of one strain of Streptomyces coelicolor Müller and one strain of S. fradiae ISP5063.