The present report deals with the hybrid vigor of rice, found in a hybrid between SHINA No.2 and NANGKING SHAN-TO. Hybrid vigor occurred in some characters such as plant height, length of culm and ear, number of ears, grains per hill, diameter of culm, and size of grain. In general the growth of F_1 plants were more vigorous than the parental plants, namely the significant increases were 19.5% in culm length, 15.9% in total length of culm and ear, 16.7% in plant height, 20.0% in diameter of culm, 28.8% and 61.3% in grains per ear and hill in each other. But the increases of ear length and number of ears per hill were not significant. On the contrary, sizes of grain of F_1 was somewhat smaller as compared with that of parental plants
