Although simazine application to flooded soil at flowering time increases the percent protein in the rice grain, it is accompanied by a decrease in grain yield which can be attributed to increased sterility. This decrease in grain yield consequently lowers the total grain protein production per crop. Application of simazine to young rice plants grown in culture solution increased the nitrogen content of the blades, sheaths plus culms, and roots. The increase, however, is not the result of an increase in nitrogen uptake by the rice plant. The reduction in dry weight accounts for the increase in percent nitrogen.