Objective & Methods: To evaluate the in vitro synergic effect of Eunkyo-san, a traditional poly-herbal formula used in the treatment of respiratory diseases in oriental medicine with quinolone antibiotics, represented by ciprofloxacin (CPFX), which was used in the minimal concentration (MIC), $MIC_{50}$ and $MIC_{90}$. of single use of quinolones in concomitant treatment with Eunkyo-san against 9 strain$ of gram positive bacteria. Results: In. the case of aerobic gram positive bacteria, the MIC, $MIC_{50}$ and $MIC_{90}$ against Staphylococcus aureus, Staphylococcus aureus smith, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus pneumoniae Type I, Type II and Type III were significantly decreased in concomitant treated groups with Eunkyo-san compared to those of single treated groups of CPFX, respectively. However, no significant changes were demonstrated against Bacillus subtilis and Enterococcus faecalis. Conclusion: The in vitro antibacterial activity of CPFX were increased against some strains of gram positive strains, especially, pneumococcus such as Staphylococcus and Streptococcus, by concomitant use of Eunkyo-san.