Field experiments were conducted to clarify the protein content of milled rice as affected by the amount of nitrogen (N) in grains and grain weight from 1990 to 1996 using two cultivar varieties (Sasanishiki and Haenuki). Both varieties showed the same response. The results obtained were as follows: 1. Negative correlation between the amount of N in the rice plant at heading and N use efficiency (here defined as number of grains/amount of N in the plant at heading, NUE) was observed. A linear relationship between protein content in milled rice and NUE was observed. 2. There was a linear relation between amount of N in the plant at heading/number of grains and amount of N in the milled rice. 3. A negative correlation existed between protein content of milled rice and grain weight when the amount of N in the rice plant at heading was less than 13.0 g m^<-2>. 4. Increased grain weight resulted due to a decrease in the protein content of the milled rice if the amount of N in the milled rice was the same. Furthermore, the same trend was observed if N use efficiency of the grain number was the same.
