The severity of rice stem rot ( Leptosphaeria salvinii) was decreased when the plant had been affected with dwarf disease virus (Oryza virus 1). Both respiration rate and activity of respiratory enzymes (ascorbic acid oxidase, cytochrome c oxidase, catalase, and peroxidase) of rice plant were found to be promoted when the latter was affected by the dwarf disease. Considering the results that the severity of the stem rot w as increased with the advance of the ripening of rice plants, it was concluded that the resistance against the stem rot of the dwarf diseased plant was caused by the vigorous metabolism of the rice stem tissue affected with the virus till the season of ripening stage of plants.