The antimicrobial activity of seventy five ethanol extracts obtained from 67 different kinds of plant species of the Mongolian flora were evaluated by means of the disc diffusion method against five species of microorganisms, Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, Micrococcus luteus and Pseudomonas aeruginosa. Among the plant extracts examined, 34 kinds of extracts demonstrated significant antibacterial activity against one or more species of microorganisms, respectively. Especially, the root extract of Paeonia anomala, the whole herb extract of Myricaria alopecuroides, the whole herb extract of comarum zalesovianum, the whole herb extract of Agrimonia pilosa and some other plant extracts demonstrated a particularly potent antimicrobial activity. The ethylacetate fractions obtained from the whole herb extract of Myricaria alopecuroides and from those of Sedum aizoon, Paeonia anomala, Sedum hybridum and Dasiphora fruticosa exhibited a particularly potent antibacterial activity especially against Staphylococcus aureus and Micrococcus luteus.