Occurrence of sheath rot rice caused by Acrocylindrium oryzae on indica varieties, IR lines and IR varieties was light to moderate in the field, whereas generally none of the recommended japonica varieties showed the disease. In general, percentage infection in the field agreed with that obtained from seed inoculation tests made in the laboratory. Culture filtrates of the fungus inhibited the sprouting of seeds of rice, barley, wheat, rye and rape. A new variety, Tongil obtained from a hybrid between japonica and indica was inhibited significantly more than was Jinheung. Conidial germination of Pyricularia oryzae was inhibited by the filtrate while no inhibitory effects were found on conidia of Cochliobolus miyabeanus.