In order to determine the effects of nitrogen application on ABA content of rice plants and their ozone-sensitivity, ABA production and ozone injuries were observed under different levels of nitrogen application with two Japonica and two Japonica × Indica type varieties. 1. In all varieties, endogenous ABA content decreased with the increasing level of nitrogen applied, although total nitrogen content increased with the increasing level of nitrogen applied. 2. Ozone injury was found to increasing level of nitrogen applied and to change depending on the varieties. Ozone injury was found to occure seriously with increasing nitrogen content in Jinheung and Nongback, however less pronounced in Tongil and Milyang No. 23. 3. Endogenous ABA content and ozone-sensitivity were related to the nitrogen content in the rice plants.