To investigate the effect of large patch infection on oxidative stress induction, super-oxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were compared between pathogen-infected and healthy (control) zoysiagrass. The sampling for leaves and roots were carried out every 2 days for a period of 6 days. The SOD activity was not significantly affected by pathogen-infection until day 2, but significant increase of both leaves (+48%) and roots (+49%) were observed at day 6 compared with control. The CAT activity was remarkedly increased by +25% in leaves and +101% in roots within the first 2 days and then rapidly decreased. The POD activity in pathogen-infected leaves was significantly increased by 74% at day 6. The increase of POD activity in pathogen-infected roots was 2-fold higher than that of the control at day 6. These results indicated that large patch-infection induce oxidative stress, and that SOD-CAT-POD antioxidant system of zoysiagrass was effectively operated.