To evaluate the antibiotic effects of cefathiamidine combined with vancomycin, netilmicin, amikacin, ciprofloxacin, levofloxacin
or
gatifloxacin respectively against 90 strains of Grams positive cocci. The protocol was designed by checkerboard method and the MICs of cefathiamidine alone and combined with other 6 antibiotics against the 90 strains of Gram positive cocci (30 strains of Staphylococcus aureus , 30 strains of Staphylococcus epidermidis , 30 strains of Enterococcus faecalis ) were determined by broth dilution method; the FIC index was calculated according to MIC results. The MIC 50 of cefathiamidine was reduced significantly when combined with vancomycin, netilmicin, amikacin, ciprofloxacin, levofloxacin or gatifloxacin. The percentage of the FIC index less than 0.5, from 0.5 to 1, from 1 to 2, more than 2 was 60%～90%, 10%～13.3%, 0, respectively. Results suggested that synergy and additivity of cefathiamidine combined with vancomycin, netilmicin, amikacin, ciprofloxacin, levofloxacin or gatifloxacin respectively against 90 strains of Gram positive cocci were primary in action, and there were little autonomy and no antagonism.