Each component of the heat balance equation was obtained independently for 24 days in winter and 8 days in summer in 1980 at Mizuho station, East Antarctica. In winter, net radiation QNR was -37.6W/m-2 , QS; +36.7W/m-2 and QC; +2.5W/m2 QL was three orders less than QS. In the summer, QNR; +l9.9W/m-2 QC;-7.4W/m’, QL ; -.SW/m-2 and Q C; .2W/m-2. In the winter cloud amount was an important factor determining the variation in heat balance components, but also variation in the strength of the katabatic wind had effect. Condensation of water vapor occurred in winter and sublimation in summer: summer sublimation had a significant effect on the heat balance. The small condensation may be due to the structure of the temperature inversion at Mizuho which is related to the katabatic wind. The present results show that at Mizuho, the radiation loss Q NR and Q S which compensate it is larger than at any other site on the continent excluding the coastal stations.