Chloramphenicol (CLP) at slightly inhibitory concentrations (3-5 microgram/ml) suppresses the inhibition of DNA synthesis and cell division caused by the temperature sensitive mutation dnaE486 at the nonpermissive temperature. Some other mutations can also be phenotypically suppressed by CLP. A similar effect is shown by chlortetracycline. Phenotypic suppression is caused by both these drugs in different cases than by streptomycin.