It was intended to investigate a relationship between Quercus mongolica and its variety, var. grosseserrata occurring to Korea and Japan. Through studies on chemical and morphological characters of 300 specimens collected from 12 natural populations in Korea and Japan, the following results were obtained. 1) The paper chromatography profiles of flavonoids (phenolic compounds) and the morphological leaf characters were closely related each other. 2) Quercus mongolica var. grosseserrata in Japan exhibited a regression line (Y - 0.824X + 16.650, r=0.64), which linked with Q. mongolica and Q. serrata, using LDP (leaf depth percentage) and Leaf angle. 3) The Width/Length ratio in fruits of pure line was significantly higher (nearly 1.0) than that of putative hybrids. 4) The leaf shape in Japan followed closely the obovateness along northward, and in Korea was found that they showed two groups within same populations, that was, ellitical and obovate leaf form. 5) Minor phenolic variation between populations was detected in Korea and Japan, and could be used effectively as a determinant of hybrids. 6) Q. mongolica originated in the northern part of Asia migrated gradually toward south and east, which developed into 4 groups, 1. Mt. Halla-Jiri region, 2. the other Korean region, 3. Hokkaido region, 4. The other Japanese region by mixing Q. serrata. 7) It was proved that Quercus × grosseserrata B1. were right treatment than a variety of Q. mongolica. However, those collected in Japan appeared to be closer to Q. serrata, while those of Korean were closer to Q. mongolica in appearance.