This study was aimed to screen edible herbs which control the composition of intestinal microflora. With in vitro experiments, we screened the water or ethanol extracts of about 60 edible herbs and wild plants in terms of the inhibition activity on the growth of the harmful Clostridium perfringens and growth promoting activity for the beneficial Bifidobacteria. The water extracts of mugwort and small water dropwort inhibited the growth of Cl.perfringens both in agar diffusion method and broth culture. On the other hand, the water extracts of petasites, mugwort, yellow day-lily and bitter cress have shown the promotion effect on the growth of Bifidobacterium longum. In the culture test using human feces as starter, the extracts of the above selected herbs increased the population of Bifidobacteria and Lactobacillus while they reduced the numbers of Cl.perfringens and E.coli.