RWJ-416457, a novel oxazolidinone, had modal MICs of 0.5 to 1 microg/ml for linezolid-susceptible staphylococci and enterococci, versus linezolid MICs for these organisms of 1 or 2 microg/ml. RWJ-416457 MICs for mutants with 23S rRNA mutations were 2 to 32 microg/ml, versus linezolid MICs of 8 to 64 microg/ml; actual values reflected the proportion of gene copies mutated.