The effects of indole-related compounds on infection behaviors of Bipolaris oryzae in onion epidermal cells were investigated. Tryptamine inhibited dose-dependently all stages of the infection behavior such as spore germination and infection-hypha formation. Furthermore, antifungal activity of some indole-related compounds to B. oryzae was investigated on the TLC plate. As the result, in the indolyl-３-butryric acid and indole-３-acetnitrile, the larger size growth inhibition zone of B . oryzae was observed in comparison to the tryptamine, oxindole, gramine, indole, indole-３-acetic acid and indole-３-acetamide. However, in the tryptophan, growth inhibition zone of B . oryzae was not observed on the TLC plate. These results suggested that accumulation of high levels of tryptamine or some indole-related compounds might be utilizable to
protect with fungal disease by B . oryzae.