During two years period of 1956 and '57, we tested the resistibility to low temperature at secdling stage and the sensitivity of heading to high temperature on 27 varieties of upland rice, comparing with 27 varieties of paddy rice. ( 1 ) On the resistibility to low temperature for the growth injury at seedling stage, generally speaking, upland rice varieties are weaker than paddy rice varieties. varietal differenes of upland rice are wider than those of paddy rice. The degree of this resistibility does not concern lvith earliness or lateness of heading time and latitude of cultivated regions of the varieties in this experiment. ( 2 ) The degree of sensitivity to high temperature for thc response of heading in uplanrl rice is the same as in paddy rice, in this experiment. Varietal differences of paddy rice on the sensitivity to temperature are wide, and the degree of this sensitivity has minus correlation with earliness or lateness of heading time, but these appearances are not noticed on upland rice varieties. ( 3 ) It is seemed that the number of days hastened of heading by high tempcrature is the same with the sum of the number of days hastened of leafing before differentiation of young ear and shortened by decrease of leaves under high temperature.