The activities of linezolid, a new oxazolidinone, and various antibiotics (penicillin, imipenem, vancomycin, teicoplanin, levofloxacin and fusidic acid) against 170 Gram positive cocci including methicillin susceptible –and resistant Staphylococcus aureus strains (n=60), methicillin susceptible - and resistant coagulase negative staphylococci (n=40), enterococci (n=50) and pneumococci (n=20) were tested by microdilution method. All gram positive cocci tested were found to be susceptible to linezolid, vancomycin and teicoplanin. The MIC₉₀ values for linezolid was not influenced by susceptibility to other antimicrobials. Linezolid was active against staphylococci irrespective of methicillin susceptibility (MIC₉₀ 1-2 μg/ml). Enterococci, including penicillin resistant E. faecium strains, and pneumococci, including penicillin resistant strains, were all susceptible to linezolid (MIC₉₀ 2 and 1 μg/ml respectively).