Methanol extracts from 84 Indian plant samples (50 species in 31 families) and 27 African plant samples (20 species in 12 families) in vitro were tested for their growth-inhibitory activities against Bifidobacterium bifidum, Bifidobacterium longum, Lactobacillus acidophilus, Clostridium perfringens, and Escherichia coli, using a paper disc agar diffusion method under O₂-free conditions. The responses varied with bacterial strain, plant species and plant part. Extracts from Cymbopogon citratus whole plants, Ocimum basilicum whole plant, Madhuca indica flowers, and Aegle marmelos leaves among Indian plant samples moderately or strongly inhibited the growth of Cl, perfringens whereas moderate growth-inhibitory activity against E. coli was obtained from extract of Indian O. basilicum whole plants. These plant extracts did not affect the growth of the lactic acid forming bacteria tested. These results may be an indication of at least one of the pharmacological actions of these tropical plants.