This study showed excellent activity of makrut leaf oil and makrut oil against many respiratory bac- teria at the various activity levels. The results of disc diffusion were not highly correlated with MIC and MBC. Disc diffusion is a screening method usually used as a preliminary check for antibacterial activity prior to the more detailed study in liquid medium to determine MIC and MBC. There are many factors that may affect the results of disc-diffusion test, e.g., volume of essential oil placed on paper discs, thickness of agar, diffusion ability of oil in agar, and variation of essential oil concentration. Therefore, disc-diffusion method is not suitable for comparison the efficacy of essential oil. The broth microdilution method measures the strength of antibacterial activity and better be used for comparison.