A study has been made to estimate biomass and NPP based on equation form of Wt=aD^bH^c for Quercus variabilis and Quercus mongolica natural stands(Mean age; 67, 62yrs old) in Chungju. Equation form of Wt=aD^bH^c was more adequate than Wt=a(D²H)^b and Wt=aD^b for the estimation of the biomass and NPP. Individual biomass was compared using a paired t-test by tree component which showed no significant differences. Total aboveground biomass of Quercus mongolica was 130.6 t/㏊ and that of Quercus variabilis was 137.4 t/㏊. Biomass of Q. mongolica was composed of foliage 5.1 t/㏊(3.9%), dead branch 3.5 t/㏊(2.7%), live branch 29.7 t/㏊(23.0%), bolebark 16.2 t/㏊(12.5%), and bolewood 74.9 t/㏊(58.0%), and that of Q. variabilis was composed of foliage 3.8 t/㏊(2.9%), dead branch 2.9 t/㏊(2.2%), live branch 24.3 t/㏊(18.4%), bolebark 20.4 t/㏊(15.5%), and bolewood 80.4 t/㏊(61.0%). Net primary production was 10.0 t/㏊/yr in the Q. mongolica stand and 8.6 t/㏊/yr in the Q. variabilis stand, respectively. Net primary production of Quercus forest in Chungju was very close to the mean NPP of the broadleaved forest of temperate zone.