Rice blast fungus, Magnaporthe grisea (race KI-197), was exposed to ozone at 300ppb/hr for 0, 8, 16, and 24 hours. Ozone exposure was started from 3 days after inoculation on oatmeal agar plates. The four ozone treatments had no detrimental effects on the hyphal growth for 4 days (p=OA07 - 0.717) after finishing the ozone exposure. Conidia in each plate were collected after the last measurement of the hyphal growth. The numbers of spores were 2.9 105-4.2 105 spores/me in each treatment, but not changed by the ozone treatments (p=0.849). The size of spore was 5.1-5.2 pm wide and 18.1-18.6 pm long, but ozone did not change either width (p=0.846) or length (p=0.734) of the spores. The spore suspensions were incubated for 16 hours at 20·C , then the percent of germination and appresorium formation were measured as 82-93% and 17-22%, respectively. These percent data were transformed to arc sine for statistical analysis. Ozone did not change either germination (p=0.618) or appresorium formation (p=0.902). Because 300ppblhr is 3 times higher than the ozone standard and has been rarely reached in Korea, our results show rice blast fungus would be highly resistant to ozone. In addition, the fungal resistance to ozone can help interpreting the interactions among ozone, rice and the blast fungus in the field.